Was Gregor Kobel Actually Good Last Season?

A year ago, I wrote an article about how Borussia Dortmund should not pursue Swiss Goalkeeper Gregor Kobel. In it I expressed concern about his rather mediocre shot-stopping metrics, among other concerns, and urged the club elsewhere. Despite my reservations, when the club ended up purchasing him, I was still hopeful that he would help turn around BVB’s defensive woes.

Unfortunately, this season was not a good one in the defensive half for BVB. The club as a whole finished in the bottom half of the league in goals conceded, with a glaring lack of clean sheets, even against modest opponents. Despite this poor defensive record, almost none of the blame has landed at Gregor Kobel’s feet, which I think is strange, because after all, keeping the ball out of the net is by far a goalkeeper’s most important job.

When trying to explain Dortmund’s appalling defensive record this season, most fans have pointed to issues in the outfield, whether on the back line or in central midfield. They point to personnel issues, tactics, injuries, and almost anything else, but one person who I’ve never heard receive any criticism is Gregor Kobel, who was Dortmund’s goalkeeper for much of the season before himself succumbing to injury towards the end of the campaign. The rationale for leaving Kobel out of the blame is usually that he was hung out to dry - that the players in front of him all too often put him in situations where no goalkeeper could have made a save, no matter how talented.

This is something that I believe most BVB fans take for granted, but is it actually true?

Before I dig into Kobel’s shot-stopping metrics, I want to briefly touch on the other aspects of his game, namely his distribution, and box control. To put it bluntly, they’re both very good, and I have no problem with his game there. Kobel actually had the highest rate of intercepted crosses of any keeper in the Bundesliga with at least 10 appearances, and had some of the highest in terms of connecting on long passes and pass accuracy. There’s no doubt that these are all ironclad qualities of his game, but unfortunately they’re not all that a keeper is responsible for.

Strictly in terms of shot-stopping metrics, Gregor Kobel’s year was middle of the road at best. Among the 20 keepers in the league who made at least 10 appearances, Kobel ranks 13th in overall save%, 6th in goals against /90, and 12th in PSxG%, underperforming his PSxG by about 3%. While none of these metrics are bad, so to speak, they typically aren’t what an elite club that’s competing for a title would expect from its goalkeeper.

Now believe me, I have reservations about using both save% and PSxG in soccer. But I think the fact that Kobel was so unremarkable in just about every category imaginable, from save% to PSxG to goals conceded to clean sheets, suggests that some of the burden lies on his shoulders.

The common refrain is usually something along the lines of this: Kobel by and large stopped the shots that he should have stopped, while the goals he did concede were out of his control, usually because of some boneheaded defensive error a member of BVB’s back line made. While you’ll never catch me defending Dortmund’s back line this season, I actually think this is a fundamentally flawed way of looking at Kobel’s season, and goalkeeping in general. I don’t think BVB’s lackluster defense is enough to explain away Kobel’s unimpressive numbers. Allow me to explain.

How we think about goalkeeping

Okay, so I have to start with a disclaimer: much of what I’m about to write is not entirely my original thought, but something that more or less was inspired by an article I read here. The article in question isn’t about BVB at all, or even soccer, but about hockey, specifically goaltending in hockey. Even if you don’t follow hockey or have any intention of doing so, I still couldn’t recommend the article more, even if it’s behind a paywall, because I think it really challenges the way that most of us think about probabilities and shot-stopping, and I believe the points that CJ, the writer, makes, are just as applicable to soccer as they are to hockey. Hopefully I don’t butcher them too much.

It’s a long article so I won’t summarize all of it, but CJ’s key point is that we tend to think of shots in a very binary fashion: either the goalie “should’ve saved it”, or “there was nothing he could do.” While this type of analysis might theoretically make sense on a shot-by-shot basis, over a larger period of time, it tends to break down.

CJ uses a really good example to illustrate this, with basketball. The average NBA player makes about 30% of their three point shots. Therefore, you would never say an NBA player “should” ever make one individual shot; but if that player took 10 shots in a row and didn’t make a single one, it could paradoxically be completely valid to say he should have made three of them.

An easy parallel to this in football would be penalty kicks. The average xG for a penalty kick is 0.76, so the average keeper has about a 1-in-4 chance of stopping any individual penalty attempt. This is why pundits always say goalies don’t feel any pressure during PKs: because they’re not the ones who should do anything, they just need the shooter, who should score, to mess up. While this might be true for each individual penalty attempt, this doesn’t hold over larger sample sizes. For instance, if you took Kobel to the training ground and had him face 100 penalties in a row, you would never say he should have stopped any individual kick, but it would be fair to say he should have stopped around 24. If he didn’t stop any, or even if he only stopped 10 or so, that would still be a huge problem, because they’re underperforming their expectations.

“There was nothing he could do”

Another point that CJ makes has to do with how we allocate blame for goals. To illustrate my point, I’ll use an example that I’m sure will evoke fond memories for all you readers:

The goal in this clip, Bayern’s first of the match, perfectly epitomizes how so many people describe Gregor Kobel’s season. The defending in front of him was abysmal: Mats Hummels made a lazy turnover and couldn’t recover the ball from Thomas Muller before he laid a pass to an open Robert Lewandowski, who snuck a shot past Kobel to level the score.

If you were to ask any BVB fan who was to blame for this goal, they would say Mats Hummels, and I would tend to agree. The vast majority of the blame should fall on his shoulders. If it weren’t for him, Bayern never would have had the ball in that position in the first place... but does he deserve *all* the blame?

This is a screenshot from the clip above, courtesy of ESPN:

This is a tough scenario for Kobel. He’s facing one of the best strikers in the world in a partial 1-on-1 at close range. The xG for this shot was 0.57¹, and if you factor in the fact that Lewandowski was taking the shot, it was probably even higher— but it wasn’t 1, because it isn’t 1 for any shot. That’s because as tough a shot as this is to defend, it isn’t impossible. There are quite a few keepers in the world who could make a save in this situation. If you were to give Kobel a time machine and have him face this situation over and over again, you would expect him to stop some of them.

“But that’s unfair - he doesn’t have a time machine, so he isn’t capable of repeating this save over and over again!” Yes, you’re right. Let’s focus on this individual instance, then: was there really nothing Kobel could have done to stop this shot? He could have seen Akanji flying in from his right, and used that info to gamble that Lewy would go near post. He could have not fallen for Lewy’s pump fake. He could have not cheated so far to the far post. He could have charged Lewy to close down the angle or maybe just get him in his head.

Again, my point here isn’t that Kobel should have saved this shot, but that he could have. Repeated over a long enough period of time, this is how a goalkeeper can have a subpar season even without surrendering many, or even any, goals that would necessarily be considered “bad ”, or even ones that he would necessarily be blamed for. It doesn’t matter how the back line in front of him performed, because at the end of the day, Kobel’s numbers reflect one inescapable fact:

He simply didn’t make enough saves.

For this article, I watched almost every goal that Kobel conceded this Bundesliga season, and to be perfectly honest, I didn’t see many embarrassing howlers. What I did see, though, were a lot of shots that, while difficult, could potentially have been saved, or where he at least could have done better. Take this goal, against Augsburg, when he chose to try to dive for the cross, and missed completely, instead of staying on his feet to block an attempt. Or this goal, a header from close range that he let slip under his arms. Or this goal, where he hesitates to either stay on his line or come out, and allows Jonathan Burkhardt the opportunity to squeeze a shot past him. I wouldn’t classify any of these goals as howlers; in fact, all three are accompanied by woeful defending from the outfield players. If you want to argue the specifics of each goal, though, then you’re missing the point. It might be unfair to say that he should have saved any specific one of the goals that he conceded this season, but it’s completely to fair to say that, on aggregate, he should have saved more.

This is how it’s possible for a goalie to have an unimpressive season, at least in terms of shot-blocking, while still passing the “eye test.” Now I don’t want anybody to think I’m saying that Kobel had a bad season, especially given the other areas of the game where he was a net positive for the club. Hopefully with better defenders in front of him next season, he will have higher confidence and will be tested less frequently, and can become the elite goalkeeper that helps the team finally win a Bundesliga title.

1. Note — I couldn’t find the xG for the shot on FBRef so I used Understat, which is less precise. The xG might actually have been a bit higher or lower, but I don’t think that changes my point.