Goalkeepers in the EPL: Using stats and data to measure goalkeepers in English football

Liverpool keeper Alisson

For the player scouting I get asked to do not a huge amount of it involves looking for goalkeepers.

Nothing unusual about that you might say considering there are far more outfield players to look at than the man between the sticks.

When clubs are looking to sign a new keeper it requires specific scouting methods to go alongside more traditional ways of looking at his/her performances. Looking at some data and stats and then applying them to some familiar and maybe unfamiliar metrics can give a better understanding of what a certain club is looking for in a new No.1.

The Importance of Adaptation

An easy example to use is of course Is Ederson at Manchester City.

Ederson: City’s £35m capture from Benfica

Whether a keeper can adapt to a teams playing style is a big factor when recruiting.

Ederson has excellent distribution from not only his feet but also his hands , he has good shot stopping ability, his starting positions are excellent when preparing to come for crosses and on other set pieces, and that’s before we delve into his superb long ball delivery and eagerness to always be on the front foot to start counter attacks.

So what can we use to back up what video scouting is showing us?


Crosses

Depending on what you want from a keeper varies on what metrics we want to apply to get an outcome that would show us a baseline and a rough idea for which keeper would look into more and compare some video to.

A question we could ask of a goalkeeper that would be useful to look at if we were a team keen on using counter attacks or getting the ball moving ASAP would be- does he tend to come for crosses quite often?

EPL catch success so far 18/19

Above is a graphic detailing the crosses faced by keepers in the EPL and not only their catch success rates but also added in is whether we can identify any trends in whether they tend to punch the ball or prefer to catch it.

Now with all this we must bear in mind the fact that at the time of writing their has only been 4 EPL games so to make a comparison at this point in a season is pretty impossible but we are looking at how these can be applied and the longevity of the metrics. This is one of the reasons why I like to include the three other English leagues as we have a bit more of a sample size and the other is because we may find a keeper that could make a step up. This I will be covering the findings from in a post in the days following this one.

Back to the graphic and crosses and maybe predictably we can see Ederson is an early front runner. Even on last seasons evidence its clear the City No.1 likes to catch rather than punch, and for a reason, he catches to start counter attacks from short throws or his excellent, accurate long ball kicking ability.

Hugo Lloris is much the same but a surprising inclusion is Watford’s Ben Foster. The Hornets unbeaten start to the season is testament to a keeper than has had his ups and downs over the years but overall is a reasonably consistent goalkeeper. Having faced 22 crosses and successfully catching half isnt bad going but is probably expected.

Looking at some keepers, could be backed up by the following, throws?.

Choosing to throw the ball rather than lump it upfield is another sign of a team liking to play out from the back and building from throws from their keeper to a defender and this is useful when compiling opposition reports. Again Ederson is up near the top of the list but we would expect this anyway again given the style of play. Fabianski is another who tends to release the ball early but in a odd trend we see Foster at the bottom of the list possibly suggesting Watford prefer him to look long for Deeney and co. The same applies to Cardiff, Huddersfield and Brighton all long ball teams so even at an early stage of the season we can maybe identify a small trend here.

On the front foot

The trend of a sweeper keeper is more prevelant nowadays and teams are looking more and more for a keeper that is good with his feet but also willing to come off his line to deal with balls played in behind their defence.

Once more Watford’s Foster shows another quality some teams may look for. Remember these are small samples but its another valid point that Foster is happy to tidy up and come out of his area to clear up loose through balls and such like.

The importance of shot stopping

A blindingly obvious important area of goalkeeping is shot stopping so can we work out from some data how good a keeeper is in this area and if so how much has he helped his team in winning/losing/drawing games along the way?

Inspired by the excellent work of data scientist Derek Yam (@YAMiAM18) I have compiled the graphic above on measuring a keepers shot stopping ability.

The method

Adjusted save percentage is a method that shows us a level in regards to if a keeper is performing better or worse than the average keeper in the league we can calculate this by showing the difference between expected goals against (xGA) and the actual goals conceded and then dividing by the total shots on target.

Another metric that can be used is Above Average Goals Saved which is an estimate that shows if a keeper has directly cost their team goals and vice versa. This is basically calculated by using the difference of the expected goals against divided by goals conceded.

Derek’s work is exceptional in this field and has personally opened my eyes to some very accurate ways of looking at goalkeeping metrics.

The results

A minus figure on the AAGS tells us that a keeper has directly cost his team that many goals for example we can see that Petr Cech has been responsible for letting in 1.27 of Arsenal’s goals so far this season but he has faced 27 shots conceding 8 goals with an xGA of 6.73 hence the -1.27 number so we can argue either way in terms of good or bad (yes i know its only been 4 games but this is just to show the reasoning at this point) on the flip side of that we have Spurs’ Hugo Lloris who has kept out 2.64 goals with an xGA of 4.64 and facing only 10 shots and even at this early stage this is considered a good return.

In summary

Their will always be doubters around that will say whether or not it is fair and and also how to measure a goalkeeper when it comes to using data but I hope I have shown, with the help of others of course, that their are ways of using these kind of metrics to evaluate and come to a conclusion alongside more traditional scouting methods (of which i have experience of both in a professional setting, trust me it works).

So far this year already i have been impressed with Alex McCarthy and Ben Foster and although these methods are by far worth much more over a longer period of time they are still a one way of finding out which type of keeper would suit your team and there are more than the metrics and stats I have mentioned that we can use to evaluate a goalkeeper.

As I mentioned before, I will be publishing a quick article and some tables on the keepers in the Championship and Leagues 1 & 2 in the days following this one.

Gareth Cooper

GC Analytics

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