Expected models are a great way to see how a player performs against a computer model. The introduction of expected goals (xG) has become huge in the modern game as a way of seeing who’s done well in terms of their goalscoring. Today we’ll look at who outperformed their xG in the 2021-22 Premier League season and who underperformed it.
xG and ‘expected’ stats
Expected stats are used to predict events, such as expected points, and xG. They’re calculated by a computer based off human input of events that occur in a football match. For example, a computer can build up an expected points tally for the season based off a few games.
In the same way, a computer is able to calculate expected goals (xG), which is the likelihood of a goal being scored from that position. Statsbomb and other statistical sites provide this information for clubs and analysts to use. They compare the shot to thousands of others, and look at things such as: position of shot, header or foot shot, shooting angle and various other aspects.
So, what is the point of looking at xG? xG can be accurately used to measure a player’s finishing ability based on the chances they’ve had. If a player has scored more than their xG, it means they are very clinical, whereas if they’ve scored less, they’re wasteful with their chances.
The xG model
Above is a graphic that shows trends between goals and xG. As seen, the general correlation is positive with some outliers. As your xG increases, the number of goals you score also increases. Anyone above the line exceeded their xG, and scored more goals than they should’ve. Similarly, those below the trendline scored less than expected. Players like Son Heung-min, Jamie Vardy, and Kevin De Bruyne heavily exceeded their xG, hence overperformed heavily last season.
However, whilst this overperformance was a good thing last season in aiding their team, it is unlikely that it will be sustainable as players are unable to consistently exceed their xG. This tells us that some of these players will experience a drop off in goalscoring form soon.
Mohammed Salah is someone who is a wild anomaly, he’s always above the trend line every season, always scoring more than he should. His finishing ability is incredible, one of the best in the league!
Diogo Jota and Sadio Mane are both almost on the trendline, shown to be slightly underperforming. But they aren’t underperforming massively, and it just goes to show how effective Liverpool’s front three are.
Cristiano Ronaldo appears to have carried Manchester United on his back when it comes to goals. He’s not only performed well himself, but has done far better than next best, Bruno Fernandes. Last season, Bruno sat below the trendline and only scored half the amount that he did in the 2020/21 season.
Alexandre Lacazette appeared to perform terribly along with Josh King, who both accumulated a good amount of xG, but didn’t manage to convert those chances nearly as well as they should’ve.
Armando Broja is a surprising one too. The forward was firing freely at the start of the season, but dropped off heavily in the 2nd half. This drop-off also meant that his goals – xG dropped to negative, as he failed to convert the good chances that he had in the second half. This states that he scored less goals than expected, and was not clinical.
The Season Ahead
Looking ahead to next season, one would expect to see Haaland and Nunez right at the top of the xG and goals charts. The pair are prolific forwards who have scored a lot for their respective clubs.
It will be interesting to see where some of the overperformers of this season rank next season, keep an eye out for De Bruyne and Vardy especially!
