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Who is Chelsea’s best Centre Back? – A deep dive statistical review

Enough is enough. No biases, no agendas – it’s time to evaluate who is Chelsea’s best CBs by statistics. In this article, I will be exa...



Enough is enough. No biases, no agendas – it’s time to evaluate who is Chelsea’s best CBs by statistics. In this article, I will be examining the key statistics used to judge a defender to rank our current centre backs: Christensen, Tomori, Zouma & Rüdiger. There is no denying that this is an area that Chelsea needs to invest in. Lampard has largely deployed a CB partnership of Zouma & Tomori, which has partly been due to the fact that Christensen & Rüdiger have been injured for the majority of the season. Some Chelsea fans have been awaiting the return of Christensen and/or Rüdiger, some believe Zouma & Tomori have earnt their spot in the team – but what do their respective statistics say?

I will be comparing Christensen’s, Tomori’s and Zouma’s 2019/2020 season numbers at Chelsea under Lampard – whilst Christensen’s sample size is a lot smaller, it is worth noting that Christensen’s statistics are very similar to his 2018/2019 numbers as shown in the appendix below. I will also be comparing Rüdiger’s 2018/2019 numbers due to his minimal game time this season, whilst this is not a fair comparison as it was under a different manager, in different competitions and with different players, it provides a useful base comparison to our current options that we have seen this season. Inevitably, Rüdiger’s statistics should be taken with a pinch of salt, and once he plays more games this season, a deeper dive into his post-injury statistics should be evaluated. Comparatively, I will also compare Chelsea’s CBs to the 2019/2020 statistics of Koulibaly, who is most Chelsea fan’s number one signing at CB, and Virgil Van Dijk, the current best CB in the Premier League and the world.

Interceptions per game
Interceptions are a useful statistic to fundamentally look at how good a player can read the game to block the opposition from moving the ball from one player to another. Interceptions made by CBs is an interesting  statistic, as CBs are the last line before the opposition is one-on-one with a keeper, thus is it a somewhat good indication of how good a CB can defend. Chelsea’s CBs ranked by the highest amount of interceptions made per game:

1)      Zouma – 2.0 interceptions per game
2)      Tomori – 1.7 interceptions per game
3)      Christensen – 1.4 interceptions per game
4)      Rüdiger – 1.0 interceptions per game

Comparatively:
A)      Koulibaly – 1.2 interceptions per game
B)      Virgil Van Dijk – 1.0 interceptions per game

Tackles per game
Similarly to interceptions, tackles made are a sign of how good a CB is at tackling as the final line of defence, however, it is also an indication of how often a CB is required to make a tackle (same as with interceptions) based on how well a CB is protected by its midfield and full-backs, as well as which side of the pitch an opposition team predominantly attacks through. Chelsea’s CBs ranked by the highest amount of tackles made per game:

1)      Tomori – 2.3 tackles per game
2)      Christensen – 1.8 tackles per game
3)      Rüdiger – 1.0 tackles per game
4)      Zouma – 0.9 tackles per game

Comparatively:
A)      Koulibaly – 2.8 tackles per game
B)      Virgil Van Dijk – 0.8 tackles per game

Dribbled past per game
The last thing you want to see is your CB being dribbled past. Chelsea’s CBs ranked by who is dribbled past the least:

1)     Tomori – dribbled past 0.1 times per game
2)      Zouma – dribbled past 0.3 times per game
3)      Christensen & Rüdiger – dribbled past 0.4 times per game

Comparatively:
A)      Koulibaly – dribbled past 0.7 times per game
B)      Virgil Van Dijk – dribbled past 0.2 times per game

Clearances per game
You always want your CBs to be making clearances to avert danger. Chelsea’s CBs ranked by highest clearances made per game:

1)      Zouma – 4.2 clearances per game
2)      Christensen – 3.1 clearances per game
3)      Rüdiger – 2.9 clearances per game
4)      Tomori – 2.6 clearances per game

Comparatively:
A)      Koulibaly – 3.0 clearances per game
B)      Virgil Van Dijk – 5.4 clearances per game

Touches per game
How many touches a player makes per game is usually a strong indication of how often they are on the ball, which for a CB is indicative of how involved they are in playing out from the back and building up play. Chelsea’s CBs ranked by the highest amount of touches per game:

1)      Tomori – 92.0 touches per game
2)      Rüdiger – 86.2 touches per game
3)      Zouma – 82.5 touches per game
4)      Christensen – 64.5 touches per game

Comparatively:
A)      Koulibaly – 81.8 touches per game
B)      Virgil Van Dijk – 85.6 touches per game

Key passes per game
A key pass is a final pass of the ball to a player before there is an attempt at goal without scoring. Whilst CBs generally don’t have too many key passes, it is a somewhat useful indication of the quality of a pass that a CB makes, for example playing a ball over the top to a striker through on goal. Chelsea’s CBs ranked by the highest amount of key passes per game:

1)      Tomori – 0.4 key passes per game
2)      Rüdiger – 0.2 key passes per game
3)      Christensen – 0.1 key passes per game
4)      Zouma – 0 key passes per game

Comparatively:
A)      Koulibaly – 0.6 key passes per game
B)      Virgil Van Dijk – 0.1 key passes per game

Passes completed per game:
In a possession-based system such as Lampard’s that has more emphasis on a direct build-up of play, playing out from the back is important to ensure there is a quick transition to break down teams effectively. Chelsea’s CBs ranked by most passes completed per game:

1)      Rüdiger – 70.3 passes per game
2)      Tomori – 70.0 passes per game
3)      Zouma – 61.6 passes per game
4)      Christensen – 49.4 passes per game

Comparatively:
A)      Koulibaly – 61.6 passes per game
B)      Virgil Van Dijk – 64.9 passes per game

Passing accuracy:
Making a pass is great, making an accurate pass is even more important. Chelsea’s CBs ranked by passing accuracy:

1)      Christensen & Rüdiger – 91% passing accuracy
2)      Tomori & Zouma – 88% passing accuracy

Comparatively:
A)      Koulibaly – 89% passing accuracy
B)      Virgil Van Dijk – 87% passing accuracy

Long balls completed per game
Long balls are more often seen by CBs by switching play (e.g. from RCB to LW, LCB to RW) or to play a through-ball over the top of a defence to a striker to be through on goal. It is often a useful play to catch out a sleeping defence and to utilise effective movement from your front three. Chelsea’s CBs ranked by long balls completed per game:

1)      Rüdiger – 4.5 long balls per game
2)      Zouma – 4.3 long balls per game
3)      Tomori – 2.7 long balls per game
4)      Christensen – 1.5 long balls per game

Comparatively:
A)      Koulibaly – 4.8 long balls per game
B)      Virgil Van Dijk – 4.9 long balls per game

Long ball accuracy
So just how accurate are Chelsea’s CBs at playing long balls? Long balls are more often than not closed down by the opposition, thus the accuracy of a long ball is a useful indication of how good a CB is playing a long ball. Chelsea’s CBs ranked by long ball accuracy:

1)      Rüdiger – 64% long ball accuracy
2)      Zouma – 54% long ball accuracy
3)      Tomori – 41% long ball accuracy
4)      Christensen – 38% long ball accuracy

Comparatively:
A)      Koulibaly – 60% long ball accuracy
B)      Virgil Van Dijk – 56% long ball accuracy

Ground duels won
Ground duels are essentially a “1v1” on the ground where there is a “50–50 ball”, which means that any of the two players have the same chance to get the ball. It is arguably one of the most important statistics used to judge a CB, as it highlights how well they can anticipate winning a duel and their strength / ability to do so. There are two ways to analyse ground duels won, A) the number of ground duels won and B) the success rate of said ground duels. Coincidentally, Chelsea’s CBs rank the same way in A) and B). Chelsea’s CBs ranked by the success rate of ground duels won:

1)      Tomori – 3.2 ground duels won per game (77.8% of ground duels won)
2)      Christensen – 2.5 ground duels won per game (69% of ground duels won)
3)      Zouma – 1.9 ground duels won per game (59.6% of ground duels won)
4)      Rüdiger – 1.5 ground duels won per game (52.6% of ground duels won)

Comparatively:
A)      Koulibaly – 4.0 ground duels won per game (61.2% of ground duels won)
B)      Virgil Van Dijk – 1.5 ground duels won per game (72.7% of ground duels won)

Aerial duels won:
The same concept as ground duels, just aerially. The success rate of aerial duels won, rather than the number of duels won, is more important to rank a CB as a CB can make win more aerial duels per game if they face more per game, that doesn’t necessarily mean they are successful or good at it. Chelsea’s CBs ranked by the success rate of aerial duels won:

1)      Zouma – 4.3 aerial duels won per game (72.7% of aerial duels won)
2)      Rüdiger – 2.5 aerial duels won per game (52.5% of aerial duels won)
3)      Tomori – 2.4 aerial duels won per game (52% of aerial duels won)
4)      Christensen – 2.9 aerial duels won per game (51.1% of aerial duels won)

Comparatively:
A)      Koulibaly – 2.5 aerial duels won per game (61.5% of aerial duels won)
B)      Virgil Van Dijk – 5.6 aerial duels won per game (76.1% of aerial duels won)

Possession lost
How often a CB loses possession is an indication of how good they are on the ball through being composed and not misplacing a pass. Chelsea’s CBs ranked by who loses possession the least:

1)      Christensen – possession lost 4.9 times per game
2)      Rüdiger – possession lost 7.4 times a game
3)      Zouma – possession lost 9.7 times a game
4)      Tomori – possession lost 10.5 times a game

Comparatively:
A)      Koulibaly – possession lost 8.5 times per game
B)      Virgil Van Dijk – possession lost 9.8 times per game

Fouls given away
The amount of fouls given away by a CB is indicative of how good they are at making an incisive tackle. It is important that CBs making as few fouls as possible, as fouls made by a CB are often either in or around the penalty box which can prove to be costly. Chelsea’s CBs ranked by who gives the least fouls away:

1)      Tomori – 0.5 fouls given away per game
2)      Christensen & Rüdiger – 0.8 fouls given away per game
3)      Zouma – 0.9 fouls given away per game

Comparatively:
A)      Koulibaly – 1.5 fouls given away per game
B)      Virgil Van Dijk – 0.4 fouls given away per game

Conclusion
So what does this all mean? Who is Chelsea’s best CB? If you give a player 4 points for every category they rank 1st in, 3 points for every category they rank 2nd in, 2 points for every category they rank 3rd in and 1 point for every category they rank 4th in, you get the following results (see appendix for a summary of ranking and points by category):

1)      Tomori (39 points)
2)      Rüdiger (35 points)
3)      Zouma (33 points)
4)      Christensen (30 points)

This is certainly by no means a conclusive study, I’ve assumed that each category, that I have ranked each CB by, is equally weighted when it isn’t. For example, ground duels won are a far more important statistic as a CB than touches per game, however I have given them the same weighting for the ease of comparison. The eye test is important, however as fans naturally we are biased towards certain players, thus statistics prove to be an unbiased source of information to interpret.

1)   Tomori: the youngest and shortest of our CBs, Tomori has shown a lot of promise. Tomori ranks first in a number of categories which highlights how good he is at reading the game, making a tackle, as well as being able to effectively pass the ball out from the back. Tomori needs to work on his aerial duels, not losing possession and the accuracy of his long passes, but the fact that our youngest and least experienced CB is ranked first speaks volumes in respect of how good he can be, especially as a lot of his statistics are similar to Van Dijk’s, if not better in some cases! Just imagine how good he can be in 3-4 years time if he is already this good. As the statistics show, Lampard has undeservedly dropped Tomori instead of Zouma whilst trialling out Christensen. If we are to sign a new CB, Tomori arguably should be the one to pair that CB, as he is statistically our best CB and arguably has the highest potential out of our current options.

2)    Rüdiger: again, Rudiger’s statistics are from the 2018/2019 season, we need to evaluate him this season. Contrary to belief, statistically speaking, Rüdiger is our best CB at passing out from the back from based on the number of long balls he plays, the accuracy of his passes and the number of passes he makes per game.

3)     Zouma: as everyone knows, Zouma ranks well in the stereotypical traits of being a CB, ie clearing the ball, winning aerial duels etc. Contrary to belief too, Zouma has strong passing statistics based on the number of passes made per game, the accuracy of his passes and the amount of accurate long balls he plays. However, the statistics show that he needs to improve massively in a number of areas e.g. ground duels won.

4)     Christensen: probably the biggest surprise of them all based on how popular he is amongst fans, Christensen ranks the lowest of Chelsea’s CBs. Even more contrary to belief, Christensen is statistically not Chelsea’s best CB in terms of building out play from the back, based on the fact he makes the least passes per game, has the least touches of the ball per game and makes the least amount of successful long balls per game out of the four CBs. Christensen is however the most composed on the ball, giving away possession the least and having the joint highest passing accuracy, but the lowest long ball accuracy. Christensen’s 2019/2020 sample size is a lot smaller than Tomori and Zouma’s, but his statistics are very similar to his 2018/2019 numbers, which could suggest he is not as good as a lot of Chelsea fans’ think he is.

Chelsea’s best CB partnership?
Based on the statistics, a CB partnership of Rüdiger & Tomori would be the best. This is not just because they are the two highest-ranking CBs at Chelsea, but because they would complement each other very well, ie Rüdiger is statistically Chelsea’s best passer and statistically, Tomori is Chelsea’s best tackler and reader of the game, as proven in multiple categories. Of course, there is more than just statistics. An important consideration is the strength of the relationship that two CBs can form together through their communication and understanding of one another. Lampard will certainly be keen to add reinforcements in defence, but for now, he has an important decision to make in respect of his strongest CB pairing, as we cannot continue to keep switching the CB partnership so often, this unbalances the team defensively as shown by recent defensive horror shows against Valencia and Everton.

Appendix





Written by – JMH @ChelseaCentral_
Edit by – Kristen @KristenPulisic

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