#25 – Why Liverpool’s Expected Goal Conundrum Makes Sense

As the new 2020/21 Premier League season is about to get underway, a big question is whether Liverpool can replicate their utter dominance. They’ve won the league by an unprecedented margin, and it never really looked like anything else was going to happen. Not even Pep Guardiola’s Manchester City teams that have just achieved 100 and 98 points in the previous two years could come close, they hadn’t been able to maintain that pace for a third season. Liverpool have just had consecutive 97 and 95 point seasons, hoping to replicate that form for the upcoming third season.

It had been noted that despite winning the league in record time, Liverpool’s expected goals and goal difference was still not as good as Manchester City’s. This suggests the idea that Manchester City were in fact the better team over the course of the season and that Liverpool have been merely lucky to win the league by such a margin.

Using shot distance, shot times and expected goals from www.fbref.com, I’ve approximate expected goals per shot for both Liverpool and Manchester City’s 2019/20 Premier League season. The total expected goal totals across each match have been proportioned out using shot distance to approximate expected goals per shot. Per shot information allows expected goals and minutes aggregation by gamestate.

Gamestate is an important factor in contextualising football matches. Stronger teams usually spend more time winning a game than weaker teams. Teams that are winning are no longer under obligation to push forward as much, with the losing team responsible for trying to get back into the game.

Across both the 97 and 95 point Liverpool seasons in 2018/19 and 2019/20, Liverpool achieved the majority of their expected goals in winning gamestates. Notably in the recent 2019/20 season,  they actually achieved more expected goals winning by a single goal than drawing.

Whereas for Manchester City, there is a clear distinction between their 98 point 2018/19 season and the recent 2019/20 season. They have earned a much larger proportion of their expected goals at a neutral gamestate than their title winning season, they are clearly creating the chances but perhaps have been wasteful. It’s also noticeable that they create lots of their expected goals when they’re already 3+ ahead and lots more when losing than the previous year.

Now lets take a look at how long each team has spent in each gamestate across the season.

Much like the expected goals charts, the proportion of minutes played between each club suggests a clear difference in approach that each team needed to adopt. Liverpool have spent a much larger proportion of their time winning by 1 goal, whilst Manchester City spent more time Losing and winning by 3+.

They both spent a similar proportion of time at neutral gamestates, though Manchester City’s expected goals at this gamestate were much higher. This suggests more chances and shots were required to go ahead in the game, Liverpool went ahead more efficiently and spent more time ahead at +1.

As mentioned earlier, your approach can change once you are winning. You no longer need to force anything or take risks, the responsibility to equalise or reduce the deficit is on the opponents so they need to take risks. Playing with no risks allows for a higher floor in performance, no doubt being in winning positions so much helped Liverpool maintain their momentum throughout the season. When you aren’t winning, you are required to create chances and shoot more which in turn helps build up your expected goals numbers.

Manchester City built up a lot of expected goals whilst at a neutral gamestate, when they were losing and when they were 3+ ahead. At neutral gamestates, these are the goals that convert into points most easily, and Liverpool were more efficient than Manchester City. When losing, you need to create shots (rack up expected goals numbers) to get back in the games, but you’re only losing because you didn’t score the first goal. When you’re 3+ ahead, these shots and expected goals likely won’t change the points returns of the match. Manchester City spent lots of time either needing to score goals in losing or neutral gamestates or absolutely crushing teams, and little in between, which perhaps explains their ridiculous expected goals numbers.

Liverpool spend little time and expected goals to get from neutral to +1 gamestates, meaning they could spend reduced time with responsibility to take more risks. They spent little time losing and lots of time ahead +1, with little time spent at 3+. They get ahead early and then not much else happened in the game, pretty good strategy to win. They’re deserving champions and perhaps explains why their expected goals aren’t as bonkers as Manchester City’s.

@TLMAnalytics

#24 Premier League Points History

It’s finally nearing end of this current season, so I wanted to have a look at past league points totals to get some context for how this season is shaping up.

To do so, I’ve taken data from www.fbref.com for league tables for last 24 years of 38 game seasons in the Premier League. A jupyter notebook used to get the league tables and create the plots is in my GitHub here: https://github.com/ciaran-grant/premier_league_points

This post looks to investigate the following three questions:

  • How do points totals recently compare to early Premier League seasons?
  • What has happened to the gap between the champions and relegation survivors?
  • How many points do you tend to need to qualify for Europe recently?

History of Premier League Points

Looks like the top 6 have been getting more points recently at the expense of the bottom half. There are only a set number of points available across all teams, the more points the big boys get the less available for the lower teams.

Does this mean there is an increasing gap between the top teams and the rest? We’ve gone through several incarnations with a top 4, then top 6 and now arguably a top 2 with Liverpool and Manchester City.

Champions and Relegation Survival

Relegation survival has been calculated as one more point than the points achieved by 18th place for simplicity of not getting too picky about goal difference.

Only 4 times out of the 24 seasons has a team required 40 points to survive, whilst it seems around 35 will usually be enough to be safe. Of course you want to aim for more points, but this seems to bust the myth of 40 points required for survival, often less is sufficient.

The points required to become champions has increased, meaning the gap between champions and relegation survival has increased in recent years. 2016/17, 17/18, 18/19 have been 3 of the highest points totals ever, only Chelsea in 04/05 with 95 in between here.

Could just be recency bias, but Liverpool were on track for 100+ this year. They’re likely to actually get 95+ and it’s expected both Liverpool/City to get close to 90+ again next year. They’re making 90 points seem normal and is becoming the minimum to win now.

How about qualifying for Europe?

European Qualification

It’s not only the Champions that has seen a point inflation, and in line with the whole top 6 sweeping up more points looks like there’s more points required to qualify for both European competitions as well.

The last decade has seen a higher average points requirement for getting both Champions League and Europa League qualifications, with 70 points for Champions League and 60 points for Europa League.

Current Season Context

Champions Liverpool are on 93 points with 2 games left, and likely they will break 95. This will make the last 3 seasons the highest 3 totals ever by a Premier League Champion. They could still win the league this year with less points than last year (97) and be in the top 4 highest points scoring teams ever.

Champions League qualification looks like coming up short of the 70 points mark. Chelsea, Leicester and Manchester United all comfortably in Europe sitting above 60 points but all to play for with 2 games left. Will be a low bar for both European competitions this year.

As for relegation survival, Bournemouth and Aston Villa both sit on 31 points with 2 games left. If things stay as they are, 32 points required for survival is the lowest since 09/10 where 31 points were needed. That year 40 points would’ve been good enough to finish 14th, this year 40 points looks good for 15th.

Final Thoughts

This season seems to be getting stretched by how ridiculously good Liverpool have been for 90% of the season, subconsciously or otherwise taking their foot off the gas once the title was wrapped up. Apart from prime Messi/Ronaldo Barcelona and Real Madrid teams, I wouldn’t expect many teams even get above 90 points, let alone dream of nearing 100.

Are these points totals also consistent across other 38 game seasons in France, Italy and Spain? How does this change when you consider Germany’s 34 game season or the 46 game seasons in the Football League?

@TLMAnalytics

#21 A View of the Suspended 2019/20 Season by Shots

Here’s a quick look back to see where the suspended seasons were left. I’m going to take a look at how efficient teams have been at converting shots into shots on target whilst simultaneously limiting shots on target against. How many shots a team takes is the most basic indicator of attacking output. You don’t shoot, you don’t score after all. Shots on target goes a step further to add a qualitative element to the shots. You don’t shoot on target, you don’t score.

If shots are indicative of how likely a team is to score and shots on target are even better, then we can also turn that around defensively. To win a game you need to score more goals than the opponent, which means that as well as trying to score yourself, you need to prevent the opposition from scoring. Reducing the shots conceded likely reduces the chances to concede a goal, and reducing the shots on target conceded does even better.

During a game, teams will try to maximise their own chances of scoring and reduce the opposition’s chances of scoring at the same time. A measure that captures both aspects of this sufficiently is known as the total shots ratio, with a respective total shots on target ratio as well. For a specific game, the total shot ratio is calculated for each respective team below:

Total Shot Ratio = Shots by Team / Total Shots of both Teams

Since every shot one team takes is a shot conceded by the other team, the sum of ratios for each team will always be 1. This also means that a total shots conceded ratio can be calculated, which turns out to be equal to the total shot ratio for the opposition in a single game.

This measure considers the proportion of shots you take against the total shots in a game. This means that if both teams have lots of shots, then the match is more likely to be equal. Whereas if one team takes lots of shots AND stops the opponent from taking lots of shots then that must be better, which is reflected here.

I’ve taken the shot and shots on target information for each match so far in each league to calculate the total shot ratio and total shots on target ratio for each match. Although not every team has played each other just yet, an average of these per game ratios was easiest to represent how each team has performed so far. Teams with high total shots on target ratios are likely to be the stronger teams in the league. Teams with higher total shots on target ratios than total shots ratios appear to be more efficient in terms of creating shots on target for themselves and limiting their opponents to just shots. Whilst teams with lower total shots on target ratios than total shots ratios seem to adhere to quantity over quality when it comes to shot selection or are susceptible to concede lots of shot on target.

Below are the results for each league, they seem to be pretty good approximations for the current league tables and manages to potentially group teams into tiers.

La Liga

La Liga 2019/20 – Total Shots Ratios and Total Shots on Target Ratios
  • Barcelona and Valencia are both getting a much higher proportion of shots on target in their matches, suggests that they perhaps are hesitant to shoot and rather manufacture better chances. Or they are great at limiting their opponents to settling for off target shots
  • Sevilla, Eibar and Espanol are at the opposite end of the spectrum, pretty inefficient at both ends
  • Real Sociedad are deserving of their top 4 place and Bilbao arguably should be better off than their mid table place suggests

Serie A

Serie A 2019/20 – Total Shots Ratios and Total Shots on Target Ratios
  • Yet another reason why Atalanta are so good this year, they create shots on target at a higher rate than their opponents more than anyone else in the league
  • 2nd down to 7th consists of the remaining European challengers and Sampdoria, who actually sit 16th! Potentially unlucky to be that far down based on shot counts

Premier League

Premier League 2019/20 – Total Shots Ratios and Total Shots on Target Ratios
  • Man City and Chelsea lead the way but are both pretty inefficient considering their shot dominance.
  • Liverpool have clearly been the best team in the league and are 3rd here, with a suggestion they have been one of the more efficient teams. This goes to show that game state can have an impact on shot counts.
  • Doesn’t look so good for Tottenham/Arsenal who are actually below 0.5 for Total Shots on Target Ratios, either by chance or design they both aren’t getting shots on target as much as top half sides expect let alone Champions League teams.

Ligue 1

Ligue 1 2019/20 – Total Shots Ratios and Total Shots on Target Ratios
  • Lille are way up there almost with Paris which bodes well for them!
  • Lyon look to be an efficient mid table team, which goes with their below par season so far. Expected them up with Marseille/Lille at least.

Bundesliga

Bundesliga 2019/20 – Total Shots Ratios and Total Shots on Target Ratios
  • Top 4 looks as expected, with Gladbach’s incredibly efficient shot to shots on target helping them keep pace.
  • The bottom half seems to be pretty inefficient, Hertha don’t appear to like shooting on target that much..

All data from: http://www.football-data.co.uk

@TLMAnalytics

#14 What Defines a Successful Season?

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No matter what happens, Liverpool’s season is a success.

With the best Premier League title race going down to the last day of the season, it’s a large contrast to last season where Manchester City had the league wrapped up and were aiming for 100 points. They became the Premier League team with the most points in a season, beating Chelsea’s 04/05 95 points by 5 points, arguably becoming the most successful Premier League team. They were so good that it’s not such a surprise that this year Manchester City are on 95 points with a game to play, potentially getting 98 points and becoming the team with the second most points scored the year after smashing the record last year. The surprise of this year is that despite Manchester City being so good, the title is still going down to the final day. Liverpool have got 94 points with a game to play and a win will bring them up to 97 points, becoming at least the team with the third most points, depending on how Manchester City’s game turns out. We are likely seeing two of the top three premier league sides ever in the same season, with the best team being one of these teams last year! It’s truly an incredible season and hopefully we appreciate how good these teams are.

This brings us to the imminent question and judgement on the whole season that comes from these last games. One team will be champions and one team will not. One team’s season will be a success and one team’s won’t. That may seem unfair since as discussed, these could be two of the three best teams to be seen in the Premier League.

However, there are of course more trophies to be won and means to success than just the Premier League. Manchester City got 100 points last year, on course for 98 points this year, have already won the Carabao Cup, Community Shield and are in the FA Cup final. They are on course for the domestic treble and the only team to get more points than them in a season were themselves last year, but they got knocked out of the Champions League quarter-finals to Tottenham. Which people are keen to focus on, despite domestic success once again Manchester City failed in Europe. The criticism is fair, Manchester City were favourites to beat Tottenham over two legs but they didn’t, largely due to prioritising the league over their first leg match. That’s where the problem with success lies, Manchester City were going for the Quadruple and looks likely they will have to settle for a domestic treble. This just shows how high their standards are and what perceived success is for a team of their quality. With two games to go, one in the League and one in the FA Cup final, from here they expect to go on to win both. However, if they don’t they already have the joint second highest points total and have won the Carabao Cup, this is probably not successful considering how close they got to all of their goals but is one hell of a season with all the chance to do the same again next year.

In comparison and with the incredible Champions League semi-finals just behind us, Liverpool have made it to the Champions League final for the second time in two years and are favourites to win this time against Tottenham. Liverpool are in contention to win the Premier League and the Champions League this year, that is an incredible achievement in itself. They lost to the Real Madrid three-peat side with Cristiano Ronaldo and without Mohamed Salah last year, as expected. Most teams don’t get to a single European final, let alone get to back to back finals. They have managed to beat Paris St Germain, Bayern Munich and Barcelona on their way to the final, even with Lionel Messi largely pulling the semi-final tie away from them in the first leg, they were the better team across both legs and you can’t argue they don’t deserve to be there.

As a worst-case scenario for the finish to this season, if Liverpool lose in their final Premier League match and lose the Champions League final to Tottenham, they will still have the fourth highest points total in a season and have got to back to back Champions League finals. Even at worst case scenario, you could argue that’s a successful season. They are expected to win the Champions League and beat Wolves on the final day, ultimately getting 97 points and coming second to the second-best team in the Premier League. Their expected finish to the season is definitely a success. If Manchester City were to drop points and Liverpool won the League title, doing the Premier League and Champions League double whilst getting the second highest points total in a season would cement this team among the Premier League’s best. It’s not possible to on one hand potentially be considered the best ever, but also potentially be considered to have an unsuccessful season based on 2 games of football. No matter what happens, Liverpool’s season is a success.

@TLMAnalytics

#13 The Top 4 Race

At the end of 2018, Liverpool were 7 points clear of Manchester City with the title fully in their hands after Man City’s slip up over Christmas. Tottenham were only 2 points behind City and arguably had to be considered in the title race too based on points alone. Chelsea were a further two points behind Spurs and while not honestly title contenders, they were very much in control of the final Champions League spot in fourth. Arsenal and Man Utd were in seemingly no mans land behind the top 4 but ahead of the bottom 14.

Figure 1: Premier League table @ 31/12/2018

This was halfway through the season, and it looked like we weren’t going to have a title race or even a top 4 race at all. Fast forwards ~10 more games, and things look a whole lot different. The two at the top have cemented themselves as the only title challengers, whilst Spurs and Chelsea have been dragged back into a race for fourth by the upturn in form of both Arsenal and Man Utd. It makes the remaining games of the season all the more meaningful.

Figure 2: Premier League table @ 29/03/2019

I’m going to focus on the top 4 race, with only four points separating Spurs I 3rd from Chelsea in 6th, take a look at each team’s chances and suggest who might miss out.

Spurs:  

Up until the end of 2018, Spurs were having the best season ever. Despite the fact that they are still playing Home games at Wembley, having several injury problems to Kane, Alli and not having a central midfield, they have managed to grind out win after win. It seems that after perhaps over performing the first half of the season to keep up with the top 2, they have regressed to the level that you would expect them to be in terms of points. Spurs are comfortably behind City and Liverpool but better than the rest in recent seasons, and the table now reflects that.

It has really only been the last 4 games that has clawed Spurs back, losing to Burnley and Southampton really only being the terrible unexpected results. But surround that with a loss to Chelsea and a lucky draw to Arsenal, two rivals for the top 4 and 1 point out of 12 will stop any team in their tracks.

Looking forwards, Spurs have still got to play away to the top 2, so could have a huge influence on where the title goes. But these aren’t the games that they should be worrying about. Moving into a new stadium midway through a season isn’t the norm and considering they have 5 winnable home games left, how well they settle into New White Hart Lane will determine whether they comfortably remain in 3rd or make things hard for themselves and rely on the rest faltering too.

Still in the Champions League, however they face Manchester City in the quarters so wouldn’t rely on that too heavily.

Arsenal:

So far, the first season without Arsene Wenger hasn’t gone as bad as it could have, they have always been comfortably a top 6 team but it was still a question whether they would be able to challenge for top 4. They seem to be one of the most polarizing teams when playing home or away this season. The last time they didn’t win a home game was in November and the last time they won an away game that wasn’t Huddersfield was in November. Arsenal at the Emirates are a completely different beast to otherwise.

In 2019, they’ve won all 6 of their home games but only 1 out of 4 away games (v Huddersfield). Admittedly drawing away to Spurs and deserving to win and losing away to Manchester City isn’t anything to be ashamed of, but losing to West Ham isn’t great. Recent form has been fantastic as a result, you know what you’ll get with Arsenal at home and anything could happen away.

Their remaining fixtures look great on paper, arguably the easiest in the league. The highest placed team they face is Wolves and they play Newcastle, Crystal Palace and Brighton all at home. Home form isn’t an issue and would expect to win all those games, however that means they still have 5 away games to play against mid table sides, the level of teams just below the top 6 but not going to get relegated. West Ham are also in that group.

To keep their top four spot, Arsenal will have to be better away from home. It’s non-negotiable as they will likely need more than 9-12 points out of the remaining 8 games.

Manchester United:

United have just appointed Ole Gunnar Solskjaer as their permanent manager, which doesn’t come as a surprise after the form that he has brought with him. After, cutting the 10-point gap to Spurs down to only 4 points in 2019 and progressing through to the Champions League quarter finals after beating Paris St Germain, it doesn’t seem like he could have done any more. The change in mindset around Old Trafford since Mourinho left has been exactly what they needed to try to turn their slow start around.

In 2019 they’ve won 5 of their 6 away games (including a 1-3 win away in Paris), losing away to Arsenal where we’ve established they’re pretty good. But only won half of their 4 home games, drawing to Liverpool and Burnley. The style of play that OGS has got Man Utd playing reflects the results pretty well, giving license to a mobile front three of Martial, Rashford and Lingard with Pogba supporting from behind is a devastating counter attacking team that relies on playing high defensive lines with lots of space behind them to exploit. Away from home it’s easier to set up this way due to the home team having more confidence, however when teams come to Old Trafford it seems as though if they set up to not to lose and deny United space in behind then they find it harder to break teams down.

This hasn’t been such a problem so far as they’ve managed to not lose when they can’t win for the most part. United only play 3 more games away from home, Wolves, Everton and Huddersfield, and you wouldn’t expect Wolves or Huddersfield to allow much space behind their defence. Whilst Everton have been much more robust defensively this year despite appearances.

With 5 games as home, they will need to improve their home form to push into the top 4. Though they will be playing Manchester City and Chelsea at Old Trafford, it will depend on how results have been up to that point but potentially all three of these teams will see these as must win games and that could bode well for United if City and Chelsea both push forward a bit too much trying to win the game.

They unfortunately have been drawn against Barcelona in the quarter final of the Champions League, however we also didn’t give them any chance against Paris St Germain and look what happened.

Chelsea:

Chelsea are a peculiar team, they have got much of the same team that has won multiple Premier League titles but every other season they seem to look disinterested. This has started to look like one of those seasons. By the end of 2018, they looked to be well established as the fourth best team in the league, however that was probably due to Man Utd and Arsenal underperforming rather than Chelsea doing anything exceptional. Since the two below them have gone on a great run of form, Chelsea haven’t been able to respond. They are an incredibly inconsistent team and it seems their performance depends on Maurizio Sarri’s mood or ability to motivate his players, which he claims he can’t.

In 2019 they’ve had pretty poor form, and not exactly for you’d expect of a top four side. They’ve won 4 and lost 4 of their last 10 games, two losses include 6-0 and 4-0 thrashings by Manchester City and Bournemouth both away from home. Aside from those, they’ve lost to Everton and Arsenal and only beaten Fulham away this year. The most worrying thing is the lack of goals, they’ve only scored 2 goals away (against Fulham) this whole year. Whilst at home looks okay at best, beating Spurs, Newcastle and Huddersfield and drawing with Wolves and Southampton.

Chelsea have a really bad problem in football away from home where they can’t seem to score goals and let in way too many. Whilst at home they can’t seem to score enough, but don’t let too many in either. Looking into more detail as to why this is happening might be worthwhile here, as they’re regularly playing (arguably) the best defensive midfielder in the world albeit out of position and an incredible controller of the game behind him. That combination shouldn’t be getting overrun in midfield.

Chelsea still have to go away to Liverpool and Man Utd which sounds scary, though they do have winnable home games and so need to win those if they want to remain in the top four race.

Overview:

Spurs – Focus on 5 winnable home games at their new stadium

Arsenal – Need to bring home form away with them as 5 tricky mid table away games remaining

Man Utd – Need to do better at home, more dominant with the ball to break down teams

Chelsea – Open up more at home to try to win games, get tighter away and don’t collapse.