#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

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.