Football data, numbers, and bias in the Premier League

Like many modern football fans, I love to look at the advanced stats that have become more commonly used over the last decade. Following on from American sports like baseball and basketball, data experts have put forth the idea that more in-depth statistics in football can be used to tell fans, coaches, and the media about a player’s contribution and team’s performance.

The problem is, as has happened this last season with Liverpool’s title win, the numbers can be read and interpreted in different ways. There are those that take Liverpool’s expected points (xPTs) and compare them against the actual points and claim they got lucky. For me, luck and fortune don’t weigh into a football player or team’s performance as much as many stats fans believe. At my son’s football training or games,  I can’t stand it when the coaches and other parents tell kids they were unlucky when a shot didn’t go in or they didn’t play well. For me, if you claim luck had anything to do with it, then you take away the skill aspect of the game (or any sport). Luck has to do with playing the lottery and not football. Does luck dictate how many goals Mohamed Salah scores or is it his hard work in training that gets him to perform on the pitch on matchday that does it?

Expected Points

Throughout the 2019-20 season, a lot was made that Liverpool’s points total and xPTS did not match up — like they were supposed to and if they didn’t something was wrong with the universe. Liverpool tallied 99 points which were 24.72 more than their xPTS of 74.28. According to the numbers (I use the great free website Understat for the numbers), Manchester City should have strolled to the title with an xPTS total of 86.76. However, the Cityzens accumulated just 81.

So, how did this happen? Jurgen Klopp’s influence cannot be calculated. There is no doubt that much of the motivation Liverpool had in games came from the gaffer pushing the club over the line.

Also, keep in mind that Liverpool crushed their expected goals (xG) number. The Reds scored 85 goals compared to their xG of 75.19. Therefore, the Reds not only exceeded their xPTS but xG as well. For me, that is the true sign of a champion, a team that exceeds what is expected. Manchester City scored right at or below the xG and xPTS. In addition, Pep Guardiola’s influence may not have been as great as in the past on a side that had won two consecutive titles. His £315 million spend on defenders prior to the 2019-20 campaign also seemed to catch up with the club as holes were still found at the back. Injuries also had to be taken into account along with motivation.

One rule for Liverpool, another for Leicester City

Cast your minds back to the 2015-16 season when Leicester City under Claudio Ranieri did the unthinkable. They won the Premier League with 81 points. That was the same figure Manchester City had in 2019-20.

Leicester City’s title win has been called the most unlikeliest, amazing, improbable, and greatest Premier League championship of all-time. Yet, looking at the numbers, Leicester City punched above their weight. And, to use a phrase thrown around by critics of Liverpool, they were “lucky”.

The Foxes xPTS for their title-winning season was just 68.94. Yet, they tallied 81 points, won the league, and have since been praised for the incredible job that occurred. But wait… Why are Liverpool criticised for their xPTS being exceeded in 2019-20 and Leicester City’s 2015-16 xPTS being praised?

For one, Leicester City were a great story coming from nowhere to win the title. They had fought relegation the season prior and came up from the Championship the season before that. In contrast, Liverpool have been on the brink of winning a title for years with several near misses. They also had more money to spend regardless of how wisely it was spent compared to other big clubs.

Which team should have won the Premier League title in 2015-16? The title should have gone to Arsenal according to xPTs. They should have accumulated 77.01 points but only took 73.53. Manchester City, who punched below their weight that season as well with plenty of managerial issues with Manuel Pellegrini, should have finished second with 70.14 points.

Leicester City’s title win, just like Liverpool’s in 2019-20, came due to players playing above their ability and a manger getting the most of the team. Opposing teams couldn’t step up on the big occasion either. Remember Spurs losing at Chelsea to give Leicester City the title?

It is easy to say the numbers tell the true story, but only part of the story is explained. The teams must still go out onto the pitch and perform with a number of factors present that are not taken into consideration — Klopp for instance.

In an interview with the Guardian, analytics expert Ted Knutson made some great points about Liverpool exceeding the xPTS model. One point was that Manchester City scored a lot of goals in certain games which weren’t always the big must-win matches. Therefore, looking at the numbers alone, it is easy to think they were the better team and more deserving of the championship.

Even fans and the media who watched the matches unfold can be fooled by this. Liverpool were not a team in 2019-20 that obliterated other sides. They took their “foot off the gas” in games once the win was secured in most cases. Think about Manchester City’s 8-0 win against Watford and 6-1 against Aston Villa, however. That’s 14 of 102 goals. Now, think about them losing to Liverpool at Anfield 3-1 or those losses to Manchester United in which goals were hard to come by. The phrase flat-track bullies comes to mind thinking about Manchester City’s big scoreline wins against bad teams.

The consitency of Liverpool was vital for the title. It is a lack of consistency that hindered Manchester City and other teams. Remember that Leicester City were title contenders up to Liverpool thrashing them 4-0 at the King Power Stadium. From there, the Foxes fell off in the second half of the campaign going from a potential league title to fifth place.

The numbers are great to look at. But without context to the season, they are just numbers thrown around. Yes, Liverpool exceeded what was expected, but that is what true champions should do.

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