Sagna, Debuchy, Jenks, and Chambers: (adjusting) By the Numbers

Bacary Sagna has had a great career at Arsenal and been a wonderful servant for the club. And now at the age of 31 (will be 32 before the season’s out) he has moved on to Manchester City’s home for wayward Gooners to collect a big final few years wages before retirement. Meanwhile, Sagna’s deputy right back, Carl “Arsenal Bedsheets Klaxon” Jenkinson, has been loaned out to Wet Hams and in so doing left Arsene Wenger free to completely reconstruct the right side of Arsenal’s defense. Wenger has done so in dramatic fashion, splashing £30m on Newcastle’s Matty Debuchy and Southampton rising star Calum Chambers. It was a bold move by Wenger, and one which I think represents an upgrade on the previous two players.

Sagna had been a player in decline the last few seasons so it wasn’t a surprise to see him let go. Earlier in the season, I tweeted a comment about how I was disappointed by how little defense Sagna played anymore. The response from my followers was an avalanche of anger. “Typical 7amkickoff” was probably the nicest thing anyone said. The stats, however, back up my observation.

What’s remarkable about Sagna’s drop in numbers is that Arsenal played more defensively this year than last. For example, Arsenal as a team attempted 138 more tackles this year over last. I would expect to see Sagna’s tackles numbers go up or stay the same but instead they dropped 0.5 tackle per game. His INT numbers went up, but so too did Arsenal’s. And you might think with this new-found defensive style, that might account for his lower crosses completed numbers but he actually tried more crosses this season than last, 123 v. 106 in 2012-13. He was, in fact, not defending as much and spending more time trying crosses.

Sagna’s aerial duels numbers, however, went up every year that he was at Arsenal. This is because over the last three years it seems like Szczesny has become more dependent on kicking the ball out to that side of the pitch. Sagna isn’t at the back heading the ball away in defense, he’s much more likely to win an aerial duel near the center circle.

This is not to say that I don’t love the guy, but rather simply that it might have been a good time to move him on.

Wenger replaced Sagna with Mathieu Debuchy and I have compared the two player’s stats in several places already. In almost all comparisons Debuchy looks like a significant upgrade on Sagna. Almost twice as many tackles, more interceptions, and (significantly) a similar aerial duels won rate and percent.

But, I hear some folks say, maybe Debuchy’s stats are inflated because Newcastle don’t have as much possession as Arsenal? The theory behind that argument goes that the team who has more of the ball has fewer chances to tackle and vice-versa. Thus, if Arsenal have 57% of possession on average, Newcastle have 49%, and Jenkinson’s new team West Ham have 43% (all true stats) then we should see a pattern of fewer to more tackles and thus we should adjust Sagna’s stats up, Debuchy’s down, and anyone on West Ham should be adjusted way down. Only one small problem: the actual numbers don’t work like that.

Arsenal attempted 1173 tackles last season, 19 more than Newcastle’s 1154, and a whopping 118 more than West Ham. Newcastle did make more interceptions than Arsenal, 596 compared to 541, but again West Ham only made 400 interceptions (141 fewer than Arsenal) all season.

Why are West Ham’s numbers so weird? I suspect Fat Sam’s anti-football. To put it bluntly, West Ham don’t do anything: they don’t pass, they don’t tackle, they don’t intercept, they don’t foul, they don’t shoot, and they don’t dribble. They are near the bottom of the table in all of those stats categories because they sit back in their shape and don’t do anything.

But the problem with adjusting stats for possession is that teams are all over the map in terms of defensive numbers. Most of the teams who lead the League in possession numbers are also some of the top tackling teams. Swansea is one of the best teams for interceptions, Man City is a top tackling team, Arsenal are oddly average, and so on. When it comes to defensive stats it turns out that teams have different “personalities”.

So, what happens if we look at a team’s variation from the League average and use that percentage to adjust a player’s numbers? In a way, try to correct for the team’s propensity to either be more or less tackly, more or less intercepty, more or less crossy, more or less passy, and more or less anti-footballish? Well, one of our readers built a spreadsheet that adjusts player’s individual numbers exactly for these tendencies.

So, let’s look at the four right backs that either played for Arsenal last year or will play for Arsenal next year: Sagna, Debuchy, Jenkinson, and Chambers.

First, passing. I won’t bore you with how important passing is at Arsenal.

Comparing Jenkinson, even on a per90* basis, is a bit problematic because his numbers are so small owing to the fact that he had just seven starts and seven subs all season. But setting aside his anomalous numbers you can see that Debuchy is very close to Sagna in each category. Chambers, who plays on a cross-friendly team, is quite the crosser of the ball. His 18% crossing rate seems low but when you consider the fact that the League average is 20% and add in the fact that that 20% counts all crosses, including dead ball situations, he’s getting in to some really decent numbers at 18% on the fly. And remember, that’s adjusted down because of his team’s propensity for crossing. His actual success rate is 20%!

On the defensive side it’s a similar story:

As I said above, Arsenal are (oddly) an average tackling and intercepting team. Newcastle and Southampton on the other hand are both very active defensive teams putting in a lot of tackles and interceptions and thus lowering what we might expect from those two players on an average team. Despite that adjustment Chambers and Debuchy are putting in some impressive numbers compared to Sagna when it comes to defense with Debuchy putting in almost double the defensive work rate that Sagna put up last season. Incredible, really, until you look up to the chart up above and note that Debuchy attempted 17% of his team’s tackles. He was worked and worked hard — and yet still able to get forward. As hard as he was worked, he punched right back.

Thus, taken as a whole, the two new players look like solid acquisitions. Chambers and Debuchy put up similar offensive numbers to Sagna and both also put up bigger defensive numbers. This paints the picture of two players who were highly active for their teams offensively and defensively and I love a hard working player.

Does that mean they will put up the same numbers for Arsenal next year?

I can’t answer that. There are too many variables at play here. Maybe teams will target the left flank more than the right next year? Maybe Chambers will be used mostly as a center back? Maybe Arsenal will win the League without putting in a single tackle or getting a single cross from the right backs?

I do know that having looked at these players numbers, having seen them play, and adjusting their numbers for their team’s “personality” I feel like both players are a significant upgrade on the players we have let go.

@7amkickoff

*Prorating a player’s stats as if they played a full 90. So, if you play 45 minutes and got 1 tackle the per90 tackles would be 2. If a player subs a lot or doesn’t play much it’s a way of raising his stats to make him more like a starter.