Premier League's Most Influential Player

[Stan]

think it's a load of bull about a formula that someone got excited about

https://www.bbc.co.uk/sport/football/40974299

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Alexis Sanchez, Philippe Coutinho, Virgil van Dijk, Riyad Mahrez, Gylfi Sigurdsson and Ross Barkley dominated this summer's transfer window.

But were they really worth all that talk?

Would Sanchez's departure have had a major impact on Arsenal's performances? Is Coutinho really Liverpool's star man? Possibly not, according to a new way of ranking players based on their importance, which tells us who really makes the biggest difference to a team's fortunes. It enables us to assess who are the most - and least - influential members of Premier League squads.

And there are some surprising results.

Ever heard of plus-minus ratings? They've been used in basketball and ice hockey for nearly half a century and are a way of identifying which players are the most valuable to their team. In those sports it tells you the points advantage/disadvantage a side experience when a particular player is on the pitch.

So, for example, when LeBron James was on the court for Cleveland Cavaliers during the 2016-17 NBA season, they could expect to score, on average, an extra 8.42 points per 100 possessions compared with when he was not in action. He was, therefore, the NBA's most influential player.

In football it follows the same premise as in the American sports - but in this new model, devised by data experts from the University of Liverpool (Professor Ian McHale), University of Salford (Dr Tarak Kharrat) and University College London (Dr Javier Lopez-Pena), it has been adapted to factor in things such as home advantage, the impact of red cards, strength of team-mates, opposing players and any substitutions that have been made.

It is also based on expected goals, rather than actual goals, as this is considered a more accurate reflection of a team's performance. So, this way, a defender's ranking isn't negatively affected by an attacking team-mate missing an open goal.

All this gives us a player's plus-minus rating which, at its simplest, compares how a team perform with a player to how they perform without them. A plus rating means the team do better with them, a minus rating means the team fare better without them. There is quite a lot more to it than that - see the bottom of this article for a more in-depth explanation. The results tell us who each team's most important - and least important - players are.

First of all, here are the 10 most influential players last season for current Premier League clubs based on this analysis. The value assigned to each player is their plus-minus rating per 90 minutes - the number of expected goals the team were better off by when that player was on the pitch. This analysis tells us Coutinho was less influential than two of the players who have been in Liverpool's attacking line-up instead of the Brazil attacking midfielder so far this season, Sadio Mane and Roberto Firmino. Perhaps Barcelona's £114m offer was targeting the wrong player at Anfield. Sigurdsson and Mahrez - discussed all summer, though only one changed clubs when Sigurdsson joined Everton for £45m - were only their teams' 10th most important players when it came to having a positive impact on their expected goal difference.

According to these ratings, Van Dijk would have been a significant loss to Southampton - he emerges as their best defender and the team were 0.96 expected goals better off per game when he played.

But Barkley, who turned down a move to Chelsea on deadline day, made little difference for Everton. His 0.04 rating was enough to put him fifth in the Toffees' list of most influential players - but was lower than every member of the Stamford Bridge club's title-winning squad.

And Sanchez, while unquestionably having a positive impact on Arsenal overall, was not as influential in statistical terms as Mesut Ozil. Or Alex Iwobi.

In fact, his 1.41 rating was lower than all of the attacking players at Manchester City, the club who came close to signing him for £60mon deadline day.

 

 

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How this system works - in detail

Take the following hypothetical example.

Alexis Sanchez plays 60 minutes in one Arsenal game, being substituted with the Gunners losing 1-0. In the next game, Sanchez comes on with 30 minutes left with the Gunners 3-0 up. He is on the pitch for 30 minutes and they score twice more to win 5-0.

From this we can work out his plus-minus rating.

Arsenal were minus one goal in the 60 minutes (-1/60) he was on the pitch in the first game, but plus two goals in the 30 minutes (+2/30) he played in the second game.

So ((−1/60) + (2/30)) × 90 = +4.5.

In other words, when the player was on the pitch the team scored 4.5 goals per 90 minutes more than the opposition.

But the key thing is how that compares with the team's rating when the player was not on the pitch.

So, in this hypothetical example, there were no goals in the final 30 minutes (0/30) of game one when Sanchez was off the field, while in game two there were three goals in the 60 minutes (3/60) before he came on.

So ((0/30) + (3/60)) × 90 = 4.5.

The rating with the player - the rating without the player = their overall rating.

In this hypothetical instance for Sanchez: 4.5 - 4.5 - 0.

That means he could be said to have a completely neutral impact - they would be neither better nor worse without him.

Are there any problems with this method?

The reason this way of rating players has not previously been used much in football is that goals and substitutions are relatively rare, whereas in basketball lots of points are scored in any given phase of a game and the set of players on the court constantly changes. This makes it easier to determine the impact a player has.

Also, in football, there are lots of factors which might affect whether a team perform better when a particular player comes on.

For example, if Manchester City bring on a striker when they are 3-0 up and the opposition are as good as beaten, his chance of scoring could be considered better than if he had started the game when the other team had something to cling on to.

And what if City were at home, only playing against 10 men and the other side had taken off their best defender to give him a rest as the game was already lost?

This is why the standard plus-minus model has been tweaked to factor in the importance of:

• Home advantage
• Strength of each opposition player on the pitch
• Strength of each team-mate on the pitch
• Red cards
• Any substitutions that have been made

Of course, this method cannot allow for everything. It cannot measure a player's influence on team morale, for example, other than by assessing how they fare when he is on or off the pitch.

It also cannot measure the effect a player has on a club from a wider perspective - a cult hero or club legend might not actually be that productive on the field any more, but for supporters having that player in the team may be symbolic, above and beyond whether their rating means they no longer merit a place in the starting XI.

Cynics may say a statistical model cannot replace a coach's naked eye or instinct, but it certainly provides food for thought for managers, players and scouts alike.

 

 

[Harry]

Yeah don't think you can read too much into that method. Iwobi being statistically more influential than Sanchez seems unlikely even in a bad month.

Mane though being our most influential is reasonable and meets my expectations. We suffered a significant slump in form when he went to the African Cup of Nations last year, and in he back of my mind when he got carded off yesterday I thought that was game over.... Had it been Salah carded off I would have been thinking we still had a chance with Mane and Firmino up front.

[Dan+]

Kante. He's yet to play a PL season without winning the league.

[Spike]

Plus minus is considered a joke in the NHL. It means absolute fuck all if a line switches out moments before or after a goal is scored/conceded. Some of the best players have terrible +\- because they play more minutes, play harder minutes, kill penalties, and play less on the power play. You can't convince me Spurgeon is a better d-man than Hedman, Karlsson, nad Weber becuase he has a better +\-

[Dan+]

25 minutes ago, Cannabis said:

I don't think anyone can argue with him being in the discussion to be honest. He's been one of the finest imports that Premier League has ever seen and wouldn't look out of place in any team. 

One of best bits of business we'll ever do signing him for £5mil. Gutted we lost him for £32mil though but we were lucky to even get that much. Only got that because Chelsea weren't in Europe.

Heartbreaking seeing him score against us

[Storts]

The answer is Christian Eriksen 

[Cicero]

Oxlade Chamberlain 

[Honey Honey]

3 minutes ago, Cicero said:

Oxlade Chamberlain 

Well I suppose it doesn't state whether it is a positive or negative influence