HomeZ OLD CATEGORIESArsenal (NN)The Slow Fade to Black of Diego Costa: Football’s Shameless Villain

The Slow Fade to Black of Diego Costa: Football’s Shameless Villain

Diego Costa is a bad man. And he looks the part. He is simply one of the dirtiest, most disgraceful, at times brilliantly skillful, talented footballers who ever slithered into the English Premier League. But he may be making a return to La Liga much sooner than planned. Here are some of the reasons.

Diego Costa Football Shameless Villain

Costa completed his £32M move from Athletico Madrid to Chelsea in July 2014. He wasted little time starting his EPL tenure by burning up the league and scoring 9 goals in his first 7 games on his way to 20 league goals before consecutive hamstring and thigh injuries in March and April ended his season prematurely. Even so, he had what could be considered an impressive first season for Chelsea. Unfortunately, however, Costa also left behind a first season stench of personal conduct as well—arguably, one of the ugliest in football.

But don’t expect any apologies from Diego. Nothing like, “Pardon a me, it was my first year. I’ll be better. Give me just a bit of time to adjust.” Nothing could be further from Costa’s defiant attitude. He makes no excuses for his tactics on the pitch. He will continue to kick you in the Achilles tendon, or anywhere else he can reach. He will even walk over your leg or hand if you are unlucky enough to be lying on the pitch, or sling a handful of mucus in your direction he just emptied into his palm from a fresh nasal-cleaning blast, and even choke, knee, or head-butt you if he can get away with it. Oh, and he’s a diver as well. Beware, he is an expert at taking a dramatic tumble, even though untouched, as if he were poll-axed by a nearby sniper if that will attract the attention of the linesman or center referee. The stylish players of Spain refer to Diego’s approach to the beautiful game as “the other football.”

Yes, Diego is a real treat. And he has no intention of ever changing the way he plays to deflect the criticisms either, since his teammates, Chelsea fans, and, especially, his club manager—even his Spain national team manager, Vincente del Bosque, have always strongly supported him. Costa has said, “I’m no cry baby. I don’t care. I will not change the way I play.”

In fact, earlier this year, then Chelsea manager José Mourinho described Costa’s offenses as “his natural style of play” and even has encouraged him to use it to “wind up” other players in hopes of having them receive yellow cards or, better, red carded out of the game as he did in the Arsenal match on September 18th of the current season in which Gabriel was sent off.

But then, this particular source of support should not come as a surprise to anyone, should it? José Mourinho, who, when as the losing manager of Real Madrid immediately after the 2011 Spanish Super Cup at Camp Nou, walked up behind the then Barcelona assistant manager, Tito Vilanova and gouged him in the eye (sic). In José’s defense, he said he was actually trying to shake Tito’s hand, but Tito was moving so fast the only thing he could reach was his eye socket. Naturally, Mourinho refused to ever apologise for this behavior.

But Diego’s strong first season with Chelsea is yesterday’s news. In football, as in almost every other highly paid profession, it’s not “What have you done for me?” … it’s “What have you done for me lately?” That brings us to the The 2015-2016 season for Diego Costa where things have been changing dramatically.

Apparently, Diego waltzed into camp a few kilos over his best playing weight. And his performance has showed it. His 20 goals scored last season (18 in open play—2 were scored from set plays) have plummeted to only 8 through week 23 of the current season (6 in open play plus 2 set piece goals). That seems a pretty steep decline by any account.

And with José Mourinho looking for work, he has no one championing his arguably mediocre season and nasty behavior, which, you guessed it, has not changed. In fact, even his behavior seemed to have spilled over to an encounter with Mourinho when his manager failed to use him as a substitute “as promised” in the closing stages against Tottenham this season causing Diego to toss his bib at him for not bringing him in. And then there was the bust-up with Oscar during a team practice. Of course, all of these were quickly dispelled as simply Diego being Diego. Good clean fun. You bet.

But maybe this snapshot call on his performance is unfair. Maybe, in fact, it’s a cheap shot. Possibly, it’s simply a bad impression and cannot be supported by “the facts.” And even though goals scored is a critical parameter, it is only one measure—there are other metrics that make a more complete picture of a striker to consider. Maybe there are mitigating circumstances and a bigger picture to examine.

A Closer Look at the Numbers

The only way to settle this is to compare the Diego Costa’s performance for a variety of important performance criteria over the last two seasons with the current one still in progress through and including week 23. This poses a small problem if we wish to look at summary data such as totals, e.g., total goals scored, total passes completed, total chances created, etc. because of the different number of match minutes Diego has accumulated during the two seasons of comparison—one completed and one, in progress. However, this potential performance comparison distortion is easily managed.

Each metric examined will be reformed to its equivalent value in either (1) number of events per 90 minutes or (2) minutes between events for the exact number of minutes played during the two seasons.

Here are the results for Diego Costa using both WhoScored.com and Squawka.com data sources.

Open play goal scoring efficiency (left foot, right foot, and header attempts). During the 2014-2015 season, Diego Costa had a 26.1% chance of converting an open play shot into a goal on his 69 shot attempts. No matter what specific shot selection he ultimately chose, his conversion rate was impressive—between 22.7 and 28.6 percent! Impressive conversion numbers for any striker.

Costa 1

Costa 8

There has been a dramatic drop off in the likelihood of Costa scoring during the current 2015-2016 campaign. The numbers have toppled to an overall goal conversion rate of 15.4%—less than 60 percent of his scoring efficiency from one season ago!! And this precipitous performance decline impacts all three scoring options.

Total goals and open play goals scored. There is no substitute for strikers when it comes to goalscoring. Either you do or you leave. An overlay between the two seasons yields the proverbial “night and day” results in terms of production as well as with the efficiency measures just covered.

During the 2014-2015 season, in term of total goals scored (including set plays and penalties), Costa was putting a ball in the net at a rate of almost one per game—every 106 minutes, and scoring and open play goal every 116 minutes. One of the most prolific in the EPL. This year is distressingly different—same aforementioned performance numbers have bloated to 199 and 266 for total and open play minutes between goals, respectively.

Costa 2

Costa 3

Passing accuracy and productivity. The number of completed passes as well as the time between key passes illustrates, again, a drop-off in both areas. The decline is more pronounced in the minutes between key passes where Costa requires 89 minutes between events as compared to only 51 in the earlier season: a 74% increase in time required but only a 5% decrease in the number of accurate passes completed per 90 minutes for the 2015-2016 season (22.5 completions) compared to the 2014-2015 season (23.7 completions).

Costa 4

Costa 5

Costa 7

Shots attempted and overall shot accuracy. Both Costa’s shot accuracy of 64% and 3.00 open play shot attempts per 90 minutes of 2014-2015 have nose dived

to 50% and 2.20 open play shot attempts per 90 over the current season.

Take-ons. Diego Costa’s dribbling success percentage dropped from an initial 39% successes rate last season to 35% this season. Unfortunately, his frequency of his attempts increased from 29.4 to 22.5 minutes between attempts during the same time span. A bad combination—like trying to compensate for bad investments by making them more frequently.

There are other parameters to look at such as fouls and defensive performance but these seem to be the most important responsibilities that Costa has had over the time he has spent at Chelsea. The picture painted from these numbers is consistent and suggests that the performance drop-off is not cosmetic and has not shown itself to be short term.

Possible Mitigating Circumstances for Costa’s Decline

Let’s face it. Diego Costa’s nose dive this campaign is not an isolated event at Stamford Bridge. And it isn’t something that happened all of a sudden.

Costa’s drop in performance between the two seasons is the result of slow-motion meltdown by a large number of key Chelsea players along with their manager José Mourinho across a broad range of measures—both offensive and defensive. And, let us not forget, it’s a year later which means that sometimes player skills are still on the rise but sometimes, well, they are not.

Here is a breakdown of two general sets of reasons for Diego Costa’s dramatic change from one of the EPL’s most productive goalscorers to one of the pack:

Directly Associated with Costa

  1. Chronic behavior wearing thin with officials. Without a doubt, Costa’s behavior has worn thin on opposition teams as well as match officials alike. He draws fouls more quickly this season than last season—about 26% faster to be specific. Last season he was called for an infraction once every 63 minutes, this season he hears the whistle an average of every 50 minutes.
  2. Supply chain drying up. Almost two-thirds of Costa’s goals relied on the steady flow of service provided by Cesc Fabregas (43%) and Oscar (21%). In fact, Cesc Fabregas led the league with 18 assists with in 2014-2015. This season, Cesc’s total has sunk to an embarrassing total of 3 assists—Costa’s main supply line has been essentially turned down to a trickle. This season Costa has been assisted on 33% of his goals from Hazard and another 33% form Fabregas—however, neither is remotely performing well and both have suffered from injuries as well as being only sporadic starters.

Problems Indirectly Affecting Costa: Overall Chelsea Team Downslide

  1. The 3-Year Mourinho Virus. José Mourinho’s personal relationships with key staff and players and his ability to offend almost everyone who had once believed in his every word. It would be foolish to dismiss the possibility that people do not enjoy working for a boss who is degrading or unappreciative of your efforts at work. And to some degree, that is what has happened at Chelsea. Who would have dreamed that Eden Hazard is likely to be sold during the summer transfer window along with Oscar and just about any other name on the roster—yet that is exactly what is on the back pages of the papers on a consistent basis over this current transfer period (along with a few other names leaving Stamford Bridge this summer). Even the once untouchable name of Thibaut Courtois is so unsettled with the high entropy situation at Chelsea that his departure is a possibility. Esprit de corp seems to be a commodity in shortage at Chelsea these days.
  1. You can’t stop the clock. All the Chelsea players are a year older and some have not weathered well. In fact, more than a few are doing quite badly, along with A comparison of Chelsea’s offensive and defensive team metrics from the two seasons reveal a story of real. Almost every side-by-side metric comparison, with few exceptions, shows how complete their downhill slide has been. When examining the cluster of defensive cluster of blocks, clearances and interceptions, a popular group metric of back line rigor, the current season rate will total 90 short of the 2014-2015 season.

A sampling of a few other indicators suggesting that events are not going well including these observations in comparing the decline of the current with previous season (Note: Two-group, binomial z-tests used with p-values ≤ 0.05 to establish statistical significance):

Costa 6

  • 14.2% decline in chances created; statistically significant, p-value = 0.0164
  • 27.6% drop in goals scored; not statistically significant, p-value = 0.1390
  • 76.2% increase in goals allowed; statistically significant; p-value = 0.0000
  • 13.7% drop in shot accuracy (shots on target); statistically significant; p-value = 0.0208
  • 11.9% decrease in number of take ons (and 6.1% decrease in take on success rate); not statistically significant; p-value = 0.1450
  • 6.0% drop in number of accurate passes; statistically significant; p-value = 0.0144
  • 17.4% drop in number of aerial duels won (as well as 7.4% decline in winning percentage); statistically significant; p-value = 0.0496


The story is one of a consistent deterioration in performance in terms of both productivity and efficiency across both offensive and defensive metrics from 2014-2015 to the current campaign. It is not a pretty picture or very encouraging for a long term London stay for Diego Costa or several other key Chelsea players, for that matter because the problem seems pervasive.

Recently, the arrival of Gus Hiddink has helped to stop the near drop into the netherworld of the bottom three Premier League table. Nevertheless, it will be quite an accomplishment if Chelsea can break into the top 8 teams let alone being able to qualify for Europe.

If persistent rumors suggesting that Costa might be traded to Athletico Madrid for misfiring Jackson Martinez are accurate, it might provide both stalled strikers the kind of change of scenery that would benefit them. If so, there will be relatively few teammates or opponents in the premiership that will be missing Diego’s company. Very few indeed. In fact, his teammate, the inimitable John Terry was quoted as saying, “The biggest bastard I’ve ever met, makes me and Ashley Cole seem like decent blokes.”

Why, John. Don’t be so tough on yourself. That’s not true. I still think you’re a bastard. And Ashley, too.

Data sources: WhoScored.com, Squawka.com

Joel Oberstone
Joel Oberstonehttp://www.twitter.com/JoelOberstone
Joel Is an avid football and modern jazz fanatic. He sees the connection between the improvisational elements of each ... the connection between Andres Iniesta and Lionel Messi as well as Miles Davis and Bill Evans. He wrote a weekly column for the Wall Street Journal Sports Europe between 2010 and 2011 using a demystified style of sports analytics to explain the details of football performance. Joel is a professor of Business Analytics at the University of San Francisco, School of Management. He is also an ardent fan of writers Mick Dennis, Barney Ronay, and Jonathan Wilson and the never-ending word wizardry of former Newcastle United midfielder Ray Hudson in his La Liga match calls and commentary.
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