One of the hallmarks of Arsene Wenger’s tenure at Arsenal has been a remarkable consistency. Consistently hailed as one of the best attacking teams in England from nearly the moment that he set foot in the marbled halls of Highbury to this very day. Consistently in Europe from his first full season onward. And consistently considered (at the least) a title hopeful. That is some achievement, especially considering the changes that the Premier League has gone through over the last 15 years. Not to mention the changes that Arsenal have undergone in that same time.
And even in the last six seasons, a time when Arsenal have been at their most inconsistent under Wenger, that consistency still shines through. You need only look at Tottenham and their travails under various managers during Wenger’s tenure to see evidence of this. If you examine the tenure of Harry Redknapp, Tottenham’s greatest ever manager, you see a club which has spent a considerable amount of money and yet finished in and out of the top four — and also failed to win a trophy.
Arsene’s overall approach to the game shows in the numbers, again, even in the most inconsistent periods, Arsene’s approach to the game is clear. Here’s a chart of Arsenal’s shots created (red), shots allowed (blue), and the difference between the two (in gold):
Oddly, that dip in the chart for the 2007-2008 season was easily the most volatile period for Arsenal over the last few years. The club lost Thierry Henry, Reyes, and Flamini and brought in Eduardo. Despite that, many still feel that had Taylor not broken Eduardo’s leg, Arsenal had their best chance at a Premier League title that season. A feeling which we will back up in a second.
I suspect that part of the reason Arsenal fans felt that 07-08 was up for grabs was because the club seemed more clinical than at any other time since the Invincibles last won Wenger a title. Looking at the number of shots on goal per game, that feeling is supported as 2007-2008 is the high water mark for that metric.
After that season, though, Arsenal have never recovered to that height and in fact, in terms of both creating chances and in terms of allowing chances have flatlined. This flatline over the last four seasons is what I suspect people are seeing when they say that Arsenal have become stagnant. Almost as if Arsenal have become too consistent, perhaps missing the flair of an Henry or Eduardo.
So, what has happened this season? Arsenal are generating roughly the same number of chances per game, they are remarkably consistent over time, and they have a flair player in Robin van Persie?
The Arsenal defense got worse. Much, much worse.
What you are looking at above is the conversion rate for Arsenal and her opposition over the last six seasons. “Conversion rate” as I am defining it is simply goals allowed or created per shot. Defensive conversion, then, is the goals Arsenal have allowed per opposition shot, while offensive conversion is the goals Arsenal have created per their shot. And difference is the, erm, difference between the two. I include blocked shots in this metric so if this differs than some other stats guy’s numbers that could be a reason why.
Arsenal’s 2007-2008 differential was the highest it has been since the Invincibles. In other words, we were scoring more goals per shot and allowing fewer per shot than at any time since 2004. This is one factor that gave Arsenal supporters so much hope in terms of possibility for winning the title.
Since that season, what you should also see is that Arsenal have been somewhat consistent offensively with their average around 11.5% of shots scored. But you will also notice that defensively Arsenal have gotten progressively worse over each of the last four seasons to the point where, for the first time in Arsene’s tenure, Arsenal have a negative differential.
Arsenal averaged 11.71% offensive conversion from 2006-2012 and 10.43% defensive conversion in that same time. This season, Arsenal’s offensive conversion is 11.46% and defensive conversion is 12.96%. That means that the negative differential is entirely down to the 13% defensive conversion rate teams are holding over Arsenal right now.
Player injury, especially to Arsenal’s defensive line have clearly taken their toll on the club this season. In addition, the early wobbles and the 8-2 and 4-3 scorelines both really hurt this metric because Man U and Blackburn scored 12 goals (of Arsenal’s total 35 goals allowed so far) on just 32 shots — 37.5% conversion.
It would be tempting for one to argue that those two games are outliers and that as such the metric is invalid. However, since Per Mertesacker went down injured at the Stadium of Blight, Arsenal have conceded 7 goals on 36 shots* for a conversion rate of 19.4%.
The alternative view here is that Arsenal’s defensive scheme has been sussed out over the last four seasons and teams know precisely how to exploit Arsenal’s defensive weaknesses. Balls over the top and set plays have been a problem for a long time.
Of course this all raises a lot more questions about Arsenal and why the defensive record is the way it is this season. Could Arsenal’s possession-based game have changed in a way that exposes the defense more than before? Have teams figured out how to exploit Arsenal’s high line better? Is there a change in football this season which puts a premium on counter-attacking? Is it simply down to injury? If it’s simply dismissed as an injury nightmare, why didn’t the club buy players to cover or change tactics to help?
Regardless of how you explain it, the fact remains that Arsenal’s defense is suffering and needs some attention.
Meanwhile, let’s hope that the offense stays healthy or that conversion differential could plummet.
*Includes AC Milan match