Following up on last week’s piece on expected goals (xG), it’s now time to focus on the defensive side of Manchester United and whether their high-profile defensive mistakes have been significantly impacting their season.
xG is a metric that assesses every chance and whether a player should have scored from that opportunity. Expected goals against (xGA) uses the same metric but focuses on the shots that are conceded by a team and whether that shot should have resulted in a goal. For example, a shot from 8 yards has a higher value than a shot from 18 yards and a shot directly in front of goal has a higher value than one from a tight angle. This then creates a statistical value of how many goals a team should have conceded correlated to the types of chances they had.
|Team||Games played||xGA||Goals against||Difference|
|Paris Saint German||31||22.14||21||-1.14|
Using understat.com, looking at the top five leagues in Europe, Serie A leaders Juventus provide no surprises conceding 5.72 goals less than expected. This highlights their effective defensive unit which has enabled them to progress to two Champions League finals in three years, but also the individual qualities of Gianluigi Buffon and Giorgio Chiellini.
Most surprisingly, La Liga leaders Barcelona concede 9.06 goals less per game than expected, even with their reputation for attacking football. Arguably, Barcelona have one world class defender in Gerard Pique showing that the defensive shape throughout the team and their high press are contributing significantly to conceding less goals and is a testament to Ernesto Valverde providing a defensive structure to a free-flowing attacking team.
|Team||Games Played||xGA||Goals against||Difference|
More impressively, the xGA statistics show that Manchester United have conceded 11.95 goals less than was expected. However, the amount of goal scoring chances conceded by Manchester United is far higher (at least 10 chances) than any other team leading a top five European league.
There is one simple explanation to this and that is David De Gea. To concede 11.95 goals less than expected shows that the defensive unit is giving away chances but the opposition are finding it difficult to score. The large difference is unlikely to account for misfiring strikers but the excellence of David De Gea. Using Wyscout, it shows that David De Gea has made 102 saves this season as opposed to 48 for Ederson at Manchester City and 63 for Thibaut Courtois at Chelsea. This is more on par with teams in the relegation battle with Lukasz Fabianski (Swansea City) making 109 saves and Matthew Ryan (Brighton and Hove Albion) 108.
The save count of David De Gea shows that he is the major factor in contributing to Manchester United’s impressive xGA, as chances are still being given away (xGA of 34.95) but goals against (23) are still comparable with teams at the summit of the top five European leagues. Overall, the statistics are pointing to David De Gea saving Manchester United’s season and being the key factor in contributing to any potential successes.