After Manchester United lost 3-0 to Barcelona in the Champions League, many fans and pundits alike were calling on the club to reinforce the backline in the summer.

A number of centre-backs have been linked with the Red Devils over the past year, but we’ve narrowed down the list to four players: Kalidou Koulibaly, Milan Skriniar, Toby Alderweireld and Fiorentina’s Nikola Milenkovic for this analysis.

If we look at the statistics for the current season, we can see some of the strengths and weaknesses in each target:

Defensive Duels (one-on-one battles where contact is made)

Wyscout has a clear winner based on this metric. Milan Skriniar wins 34% of these duels, compared to 29% for Kalidou Koulibaly, 24% for Nikola Milenkovic and just 23.6% for Toby Alderweireld.

Considering the Slovakian gets involved in at least one more duel per 90 minutes compared to the Belgian as well, he certainly shows he is a stronger defender one-on-one with opponents.

Aerial Duels

Aerial prowess is key for a centre-back, as is knowing when you can win a header against your opponent. Here we actually see Skriniar is by far the worst performer with just 43.8% of aerial duels won.

Compare that with Koulibaly (56.7%) and Alderweireld (48.7%) and you can see the marked difference. Milenkovic is well out in front here though, having won an impressive 63% of his aerial duels, which suggests if nothing else, he would be the go-to man for clearing crosses and long balls.

Tackles

This is an interesting one as there are huge differences between the four players, likely down to their different styles of defending.  While Koulibaly (0.49 tackles per 90) and Milenkovic (0.52) are far more likely to slide in than Alderweireld (0.2) and Skriniar (0.16), the success rates indicate that Koulibaly (45.5%) and Alderweireld (45.5%) are far more likely to win the ball than Skriniar (15%) and Milenkovic (25%).

Considering Koulibaly tackles more often and is more likely to win it, he is certainly the most proactive out of the four in terms of tackling.

Interceptions

In contrast to the differences in their tackle stats, the four are almost identical when it comes to intercepting passes. All of them average around 5 to 5.5 for interceptions per 90 minutes with Koulibaly (5.5) slightly edging out Milenkovic with the most. Again, it suggests the Napoli defender is more willing to step in.

Blocked Shots and Clearances

Getting in the way of shots is an important part of a defender’s job and here Koulibaly is again the victor. He averages 0.84 blocked shots per match compared to 0.67 for Skriniar, 0.51 for Alderweireld and 0.49 for Milenkovic. Clearances are pretty much the same between the four, averaging at least three per game.

So who’s had the best season? Overall I would go for Kalidou Koulibaly. His all-round game makes him the best candidate. While Milan Skriniar is excellent in one-one situations, he clearly lacks the Senegalese player’s commanding presence both in the air, and when stepping in to make tackles.

Of course, making more tackles doesn’t necessarily make you a great defender, as Virgil van Dijk’s numbers are quite low in that metric as well, but in terms of aerial ability, interceptions and defensive duels, Koulibaly would be the closest match.