In the 20/21 season, Crystal Palace had the fourth worst defence of any team in the Premier League. But they finished the following one with the fourth best. The team made some clever changes to achieve that.
Crystal Palace started the new season with a completely new centre-back duo, partnered with two existing fullbacks. They also picked a new defensive midfielder as the analytics department and coaching staff decided to give this role to a player who was previously a regular starter in a different position.
And this realignment worked perfectly. According to the xPoints metric, the team should have finished in the 6th place and had the 4th best defence based on the quality of chances conceded.
The X-axis shows the quality of chances conceded in terms of the xG metric (expected goals), the Y-axis shows the average height of defensive actions:
The centre-backs Cheikhou Kouyaté (30 years old) and Gary Cahill (34) were replaced by Marc Guehi (21) and Joachim Andersen (25). Thus, Palace did not reach for big stars - Andersen had spent the previous season on loan at relegated Fulham and Guehi at Swansea in Championship.
From having one of the worst defended central areas in its own box, Palace became the team with one of the least penetrable. Altogether with very well defending Mitchell and Ward, the defence allowed few shots from dangerous areas.
Comparison of the 20/21 and 21/22 seasons. The red parts on the map indicate spaces that are more penetrable than the league average. The blue ones are defended above average.
Much of the credit also goes to Kouyate, who was moved from the CB position to become number six. The analytical department noticed his fantastic success rate in duels and tackles and gave him the role of a destroyer in the middle of the pitch. And the experienced Senegalese has indeed become one of the best sixes in the league.