The Telegraph, not The Times, sorry!
Were Leicester really the best Premier League team in 2015-16?
By Daniel Zeqiri, The Telegraph
The league table never lies. It is one of football’s oldest adages that we have all parroted when listening to another fan’s hard luck story about their team’s season.
Except, it is not really true. We know this instinctively at the end of August, when a three-game sample size and the vagaries of the fixture list render it meaningless. Yet even across a 38-game sample, relatively small compared with the historical span of the game and our football watching lives, there is room for variance and unpredictable outcomes.
Leicester’s Premier League title win at 5,000-1 was certainly one of those, and a look back at the numbers from the 2015-16 season hammer home what an against-all-odds achievement it was (with apologies to the Phil Collins averse among you).
Claudio Ranieri’s team had the second-best attack in the Premier League with an Expected Goals tally of 69.31, only slightly more than the 68 they actually scored through Riyad Mahrez and Jamie Vardy shredding teams on the counter-attack. However, according to xG their defence was only the eighth best in the league – allowing 46.10 xG against but only conceding 36 – giving them an xG difference of +23.21.
Expected Goal difference is just one imperfect measure of a team’s abilities, but does offer a strong impression of which teams are striking a balance between defence and attack: creating a healthy volume of chances and not exposing themselves at the other end. According to this measure, Leicester were the fourth-best team in the league in 2015-16 as the below graphic demonstrates.
The disparity between the metrics and Leicester’s 81-point championship-winning season is due to their defensive overperformance, conceding 10 fewer goals than the data ‘expected’ them to. A confluence of factors can explain this: good fortune; poor opposition finishing; some outstanding goalkeeping by Kaspar Schmeichel.
It may also have been a consequence of their deep-lying defensive strategy. Teams who cede possession and look to soak up pressure tend to concede more shots than those seeking to dominate territory higher up the pitch. The cumulative effect of conceding a higher volume of shots can sometimes inflate a team’s xG against figure. The number of bodies barricading a striker’s path to goal are not always considered in xG models. When defenders of Wes Morgan and Robert Huth’s frame are throwing themselves in front of shots and making last-ditch blocks, good chances can become average ones.
What cannot be disputed is that Arsenal and Arsene Wenger have reason to sorely regret the 2015-16 campaign. According to xG, they had both the best attack and the best defence in the division albeit in a year when Chelsea, Manchester United and Manchester City all fell below expectations. How different things may have been had Arsenal signed an outfield player in the summer transfer window, Santi Cazorla not torn his knee ligaments in the autumn or striker Olivier Giroud not gone on a 15-game scoring drought after January. Arsenal underperformed their xG in attack by a shade more than five goals that season.
Elsewhere, the value of using data to make predictions about future performance is clearly demonstrated. Although Manchester United finished fifth and won the FA Cup, their miserable xG difference of +4.53 shows they were right to part ways with Louis van Gaal.