The Broken Career of Abou Diaby

Abou Diaby has, sadly, left the building. After nine years of an injury-riddled career with Arsenal, he was finally given his release.

Diaby was once seen as the brightest new star to enter the Premier League in many years. Gunner manager Arsené Wenger referred to Diaby as the next Patrick Viera — except that he was viewed as having even more impressive attacking skills than the formidable, former Arsenal captain.

But how accurate an assessment is this? Has Abou Diaby, in his checkered career of stops and starts during each EPL season, ever really demonstrated such a lofty assessment of his talents?

Although there are a number of articles providing opinions and impressions regarding Abou Diaby’s unrealised potential, none have been based on hard, numerical analysis. This one will be different.

A comparison of Abou Diaby’s performance is made — across his 9 seasons with Arsenal — with the single standout 2013-2014 EPL season of Yaya Touré using Opta match data to see, once and for all, if they look competitive or if they pale by this contrast. These data are shown in Table 1 and illustrated in Figure 1. However, there is a problem with comparing the measures of Abou Diaby’s “career” of data with the single season of Yaya Touré: the large difference between the sample sizes of these two groups of measures does not make for a convenient apples-to-apples comparison of scale.

The only way to meaningfully compare these two groups is to normalise them, i.e., restate them in terms of common units of scale. The natural imbalance that occurs because Diaby makes more than double the number of touches as Touré — 7,253 to 2,873 — can be more meaningfully compared in terms of “touches per 90 minutes” or “minutes between touches.” These normalised Opta data measures are restated in Table 2 and illustrated again in Figure 2.

Each pair of Opta measures can now be statistically tested using a two-group binomial z-test, with the results shown in the last column in terms of the p-value of the difference. Unless the difference is compelling — has less than a 5% chance to have occurred by accident — no significant difference is assumed (NSD). The color-coded results established exactly which Opta measures Diaby’s performance is equivalent to, weaker than, or superior to those achieved by Yaya Touré.

As an example, the percent shots on goal (%SOG) shows that Touré outperforms Diaby by over 10 percent (54.0% to 43.6%). Surprisingly, the p-value=0.2257 suggests there is no statistically significant difference (NSD). Why? Because it is based on a relatively small sample of total shots attempted — only 39 of 90 for Diaby and 27 of 50 for Touré. However, an interesting contrast is the comparison of the of the statistically superior difference that Touré establishes over Diaby in the number of touches per 90 minutes — 88.3 to 83.4, respectively. This difference is less than 5 touches per game, but since it is based on samples measures in the thousands, the statistical difference is highly significant (p-value= 0.0000) and the results are coded in bolded blue to indicate that, indeed, Touré was the better of the two for this metric. Now, let’s examine the entire array of Opta measures in our collection.

If Abou Diaby were able to stay healthy — if you can suspend for the moment the shattered reality of the past nine years — his pitch performance has outcomes that range from average to what can be described as remarkable.

Here, in finer detail are the findings as contrasted against what can be considered as an exceptional 2013-2014 single season performance of Yaya Touré. 

Attacking Measures

Goal Scoring.

Touré had an exceptional season and was among the league leaders with 20 goals — unusual for a central midfielder. Additionally, Touré’s shooting performance can be described as very special. His shot efficiency (p-value=0.0012) and shot quality (p-value=0.0023) exceeded every goal scorer in the Premier League — unheard of for a midfielder. His shot accuracy (%SOG) is good and is, in fact, on par with Touré’s (no significant difference) but that is the least important metric in shooting skill. Diaby averages about 6 goals a season. Nothing special for his position.

Chances created and key passes are two of the most important measures of a midfielder’s contributions to a team’s performance. This is particularly important for positions that are not called upon to be primarily responsible for putting the ball in the net but, rather, distributing the ball efficiently to those that are in the more attacking roles. Diaby and Touré had very similar numbers—no significant differences (NSD).

Dribbling success is also an indicator of a players’ attacking skills. When a player is successful at dribbling he attracts multiple defenders and creates space for other attackers. Although Diaby and Touré’s dribbling efficiency was similar, Diaby was vastly superior in the number of successful dribbles per match he would make—almost 250% more. Diaby is a dramatically more prolific dribbler than Touré (p-value < 0.0000).

Passing

Although Diaby did complete over 84% of all passes Touré had one of the highest overall completion percentages of any central midfielder in the EPL. Touré’s passing frequency and accuracy are considerably superior to Diaby’s numbers (p-value<0.0000). 

Defending Measures

Tackling and Aerial.

Diaby and Touré have approximately the same tackling and aerial defensive skills in terms of percent efficiency. However, Diaby is dramatically superior in both categories in terms of the quantities of successful defenses he makes both in the air and on the ground. Both of Diaby’s aerial and tackling numbers must be described as extraordinary.

Blocks, Clearances, Fouls Won and Interceptions.

Diaby’s composite measure of aerial, tackling, blocks, clearances, fouls won, and interceptions for Diaby are 365% superior to Touré who is considered a steely midfielder by most —an off-the-scale finding. No midfielder in the EPL has numbers remotely close to Abou Diaby’s numbers: his performance is exceptional.

Discipline Measures

Discipline.

Neither Diaby’s or Touré’s numbers suggest any discipline problems with yellow cards every 570 minutes or 6 per season (red cards occur less than one per season). The same situation for corners yielded. No statistically significant difference. However, although Diaby concedes significantly more fouls than Touré, it is still a very low frequency and of no practical importance.

Conclusion

The ability to resist injury, and to have the capacity to quickly recover, is an increasingly key quality in scouting for desirable footballers. Unfortunately, it is Abou Diaby’s short suit. The almost constantly injured Abou Diaby has proved to be Arsenal’s “man of glass” over the past decade; the football version of the Elijah Price role in M. Night Shyamalan’s 2000 movie, “Unbreakable.”

But Abou Diaby has always been willing to battle back. And because he has been so relentless, his career isn’t over just yet.

Although he has not yet been included on Marseille’s active roster, Diaby will be attempting yet another return to the pitch very soon. And any serious fan of football — no matter their favourite club — will most certainly be pulling for him to finally have a successful season for Marseille … to finish a single campaign without serious injury. And for Abou Diaby, that might even be considered a triumphant season.