Are Manchester City buying the wrong defender?

The word is that Manchester City will sign Kalidou Koulibaly from Napoli this summer, with a long-term contract and a substantial transfer fee. Koulibaly has at times been one of the best central defenders in Europe, but he's also 29 and finishing up a season where he's had a couple of muscle injuries. CBs can thrive into their thirties, but does this deal really make sense?

First let's have a look at Koulibaly's stats this season for Napoli using a Premier League standard:

His overall defending stats look pretty good – above average quality and very aggressive – but there are a couple of potential areas for concern. His ball retention is quite a bit lower than the level Manchester City usually expect of their CBs. And his skill ratings in duels are pretty average as a whole. In fact, he's looking weak on the ball, which may go some way to explaining the ball retention ratings.

A look at his smartermap this season at LCB is particularly interesting, because it's pretty unusual:

Koulibaly stays very narrow around his own penalty area and rarely gets out to the left flank to cover. But he does dribble out of the back and can pass from past midfield, generally a mix of short and long passes, but shorter as he gets wider.

These may not be the most relevant data for Manchester City, though, since they're probably looking for a player at RCB to partner Aymeric Laporte at LCB. Koulibaly hasn't played much RCB at all this season – or even in the past several seasons. In 2018-19 he had a few matches where his numbers were less than impressive:

To be fair, Koulibaly's ball retention was better at RCB, but his overall attacking and defending stats were mediocre. These are small sample sizes, though, and Koulibaly might find himself playing a slightly different role and/or style at Manchester City.

Speaking of style, we can get a better feeling for Koulibaly's overall style by comparing him to other players. Here's a side-by-side comparison with a couple of Premier League CBs who have played in a similar way:

Both David Luiz and Ramiro Funes Mori are ball-playing CBs who like to get forward, especially by dribbling out of the back. It's not clear that they're the kind of defensive anchors that Manchester City might be looking for, still trying to fill the enormous hole left by the departure of Vincent Kompany.

When we look at players with a similar style to Kompany's – here using the 2017-18 title-winning season, where he was mostly heatlhy, as the model – Koulibaly isn't anywhere near the top of the list in Europe's top five leagues. These players are:

France's U21 international Andy Pelmard has some way to go before he's ready for the Premier League, and Javier Mascherano, Javi Martinez, and Mikel Gonzalez are all quite a bit older than Koulibaly. So is Thiago Silva, but if Manchester City are bringing in a player to platoon with John Stones, then signing the veteran Brazilian – who's available on a free transfer – might not be such a bad idea.

Even more attractive, though, is the possiblity of adding a player who has already excelled in the Premier League but recently appears to have lost his starting spot. Joel Matip has been overshadowed by Joe Gomez in the second half of Liverpool's season, yet he's still among the best RCBs in the Premier League, particularly in the air. Matip's going to be 29 soon, too, and he's had his own injury issues. So who's the better fit?

First, let's look at what Manchester City expect of their RCBs. Here are the guys who played the position most in the past three seasons under Pep Guardiola:

All of them are ball-playing CBs who can dribble forward, but they do much more link-up passing than passing toward goal. They have extremely high ball retention, and they're excellent in the air in open play. Stones was hardly an aggressive defender, but Kompany and Nicolas Otamendi definitely were. Now let's see how Matip and Koulibaly compare:

At RCB, Matip is much more active than Koulibaly – though we'd probably expect Koulibaly to emulate his style at LCB a bit more under Guardiola. More cruicially, Matip is not such an aggressive passer, and he's outstanding in the air as we mentioned above.

Manchester City may well be grooming the 19-year-old Eric Garcia to take over at RCB in the long term, but that wouldn't explain why they'd offer Koulibaly a long-term contract. There's no doubt that Koulibaly is a marquee player. Yet his age, his injuries, the fact that he hasn't played much RCB in years, and his style all make this move a bit of a headscratcher. Will it really pay off?

[Photo: Clement Bucco-Lechat]

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