Does Chelsea really need a new goalkeeper to challenge?
Bringing this back to Mendy and Arrizabalaga. Two keepers have mainly been between the stickers in the last three Premier League title winning teams. Alisson (Liverpool) and Ederson (Manchester City). In the 19/20 season, Alisson Becker won the league with Liverpool, saving 72% of the shots he faced, allowing an impressive 0.8 goals per game over 29 games, and keeping 13 clean sheets, clean sheets in 45% of his games. It may surprise you then, to know that the 19/20 is not even close to being Alisson’s best season for Liverpool as a goalkeeper.
Post-Shot Expected Goals minus Goals Allowed (PSxG+/-) is a metric that can be used to judge goalkeepers based on the quality of the shots they faced after the shot has been taken. This is markedly different from xG, as xG is determined pre-shot, post-shot xG means that if a player hits a shot from 30 yards but aims it at the top corner, while the xG of that shot may be as low as 0.02, the post shot xG may be as high as 0.94.
This is considered for keepers because wherever a shot is hit from, if it’s headed for the top corner, you have a low chance of saving it anyway, so you cannot be blamed for allowing it. However if the post-shot xG is relatively low, and the keeper allows the goal, the keeper is marked down. PSxG+/- is a relatively accurate way of judging goalkeepers in addition to save percentages, it highlights the quality of the shots the keeper has faced and checks if the keeper has been good considering the shots he’s faced. Naturally the higher this number is on the positive scale, the better for the goalkeeper rating wise.
In 29 games, Alisson’s PSxG+/- was -2.3, which means that the Brazilian let in 2.3 goals more than he was expected to, considering the shots he faced. In addition to that, he made two errors leading to shots and one error leading to goal. In no other Premier League season has Alisson recorded a negative PSxG+/- score. Yet, he has not won the league in any other season, despite performing significantly better in all of those seasons.
Ederson last season (21/22), won the league with Manchester City (for the fourth time), saving 70% of the shots he faced, allowing an incredible 0.7 goals per game over 37 games, and keeping 20 clean sheets, clean sheets in 54% of his games. Yes, you guessed right, that was also not Ederson’s best performance as a goalkeeper for Manchester City, as he scored -0.3 in PSxG+/-.
What’s the point? The keeper accounts for very little in title races, and keepers on title winning teams just need to be competent, consistent and occasionally make big saves. This is because title winning campaigns are decided more by the consistency of the outfielders and forwards, and less by the “stellar” performances of their goalkeepers.
Last season, Mendy finished 3rd with Chelsea, saving 70% of the shots he faced, allowing 0.9 goals per game over 34 games, and keeping 14 clean sheets, clean sheets in 41% of his games. Mendy recorded a PSxG+/- score of -1.6, but remember that Alisson recorded -2.3 when he won the league.
Mendy and Ederson have matched themselves in save percentage in the last two completed Premier League seasons. In fact, in the 2020-21 season, Mendy and Ederson allowed 0.8 goals per game each.
Yes, shot-stopping is not all these keepers are in their teams for, distribution is also a big part of it. Ederson is the clear leader in this regard, as over the past two completed campaigns he has averaged 54% long ball accuracy and completed 66% of his chipped passes. Mendy comes in second with 46% long ball accuracy, completing 60% of his chipped passes, and Alisson is a close third matching Mendy in long ball accuracy, but completing 58% of his chipped passes. There is no reason Chelsea cannot win the league with Mendy between the sticks, his performances are consistent, his distribution is superb, and he makes big saves regularly enough that you can count on him to be decider in the odd game where you need your keeper to save you.