Why Borussia Dortmund Should Not Target Stuttgart’s Gregor Kobel

With Roman Bürki set to leave in the summer and an aging Marwin Hitz slated for a backup role, Borussia Dortmund need a new starting keeper. Of the many potential keepers that BVB have been linked to, one name that keeps coming up is Gregor Kobel. The 23-year-old Swiss keeper is currently the starter for VFB Stuttgart, and would cost BVB somewhere in the region of €16-18 million. Kobel himself has expressed interest in the possibility of moving to Dortmund, so this rumor rises above the status of mere tabloid speculation.

So is Gregor Kobel the answer to BVB’s goalkeeping troubles? While he is still young, and theoretically has room to develop, the early indicators are that he is not the elite goalkeeper to bring stability back between the pipes of the Westfalenstadion.

The key role of any goalkeeper is, of course, to stop shots from going into the net. If you look at all shots as equal, and rank all Bundesliga goalkeepers by their raw save percentage, then Gregor Kobel ranks eighth out of 19, with a 68.6 Sv%. This is slightly higher than Marwin Hitz, at 66.7%, and actually lower than Roman Bürki, who has a 68.7 Sv% this season. While only a few percentage points may not seem like a lot, if you think about it over the course of the season, it can add up: a 2% difference for a keeper that faces 120 shots can make a difference of 2-3 goals, which can easily translate to an extra win or two.

However, because shot quality can vary so much in soccer, Sv% isn’t the best metric for judging a goalkeeper. Looking at post-shot expected goals (PSxG), which measures the expected goal values of shots that a keeper faces, portrays Kobel in a less positive light. Of the 19 goalkeepers who have made more than 10 appearances in the Bundesliga, Kobel ranks 11th in (PSxG - GA)/90 with -0.13, meaning he concedes 0.13 more goals per game than a keeper would be expected to. That may not seem like a lot, but again, multiply that by thirty or so games and that’s about 4 more goals conceded than a keeper that’s merely replacement-level. Kobel’s numbers rank higher than Bürki, who’s actually second from the bottom of the league, but well below Hitz, who is actually 6th in the league this season.

There are other areas besides shot-stopping where a goalkeeper can excel. Unfortunately, Kobel doesn’t really impress in any of these either. He’s near the bottom of the league in defensive actions outside of the penalty area, meaning he isn’t an effective sweeper keeper. He’s about average when it comes to stopping crosses, ranking 9th out of 19. He’s in the bottom half of the league in his completion rate for long-range passes, below both Bürki and Hitz. Basically, of every advanced goalkeeping statistic that FBRef.com offers, Kobel is about league average or worse.

So why are BVB reportedly interested in him? I honestly have no idea. The only thing I can figure out is that he’s very young for a starting keeper, at only 23 years old. This means that, assuming his career follows the typical trajectory for a goalkeeper, he has a solid 4-5 years left remaining in his prime, before his performances start to decline. Unfortunately, there’s little reason to believe that his performances will improve much. According to Paul’s article linked above, a goalkeeper’s abilities tend to peak starting at age 23, and extend until around age 27. Theoretically speaking, Kobel’s performances this year should be some of the best of his career... which doesn’t lend optimism to the idea that his numbers will improve substantially in the future.

The only other thing I can figure is that BVB’s scouts have watched Kobel play, and believe that his fundamentals and physicality indicate that he isn’t yet playing up to his full potential. He’s certainly built like a goalkeeper, standing 6’4” with an imposing frame. To try to determine what Dortmund’s scouting department might see in Kobel, I watched match recaps of every single one of his appearances this season to identify a few of his strengths and weaknesses.

From my fairly cursory analysis, it seems that Kobel’s biggest strength is his lateral movement in the air. He’s very good at blocking shots to his left or right as long as they’re not too low: see this combination of saves against Leipzig as just one example.

He’s also good at closing down tight angles, and I didn’t notice any blatant howlers, other than one or two that he let through his legs.

Kobel does appear to have a few weaknesses. He tends to cheat a little close to his near post on crosses, so it isn’t uncommon for him to be beaten far post; see this goal against Union Berlin as an example.

I can also see why his cross interception numbers are so low. He seems to stick to his line quite a bit, only coming out if he’s 100% certain he can collect the ball. This means he’s very rarely in a position to block a cross. While this means he’s usually in a position to react to a shot, it also means he’s more likely to surrender shots off crosses in the first place.

Overall, I can see why BVB’s scouts are interested in Kobel, as he’s large and appears to be decently mobile. Unfortunately, I don’t see enough by the eye test to negate his otherwise mediocre performance metrics. There are other keepers in the Bundesliga like Koen Casteels, or other keepers around Europe like Alphonse Areola, who have much stronger numbers than Kobel, and probably wouldn’t cost much more. Given BVB’s stringent transfer budget, I believe €16-18 million could be put to much better use pursuing other transfer targets.