Expected goals - The new technology revolutionising football
Football is often a very subjective sport, many people have different opinions, however stats can back up these opinions to make arguments for liking certain players over other players stronger. The industry that is “sports analysis” is growing larger and getting more popular day by day. Analysts can work at clubs or even in the media, and in the media the words hot on everybody's lips is “expected goals” or xG.
Expected goals is a stat that is very important in modern football. xG identifies the quality of each shot or each chance created, so us football fans have the statistical answer of, “should he have done better there?”. Its introduction into this year's edition of Football Manager has also highlighted how important it is in many aspects of football.
For example, a penalty would have a much higher xG number than an outside of the box shot. If a chance had a 0.35 xG number that would mean the player should score 35% of the time.
xG also takes into consideration how the ball was struck, what part of the body the ball was struck from, where and how the ball came to the attacker, distance and angle of the shot and was it from open play or a set piece. All these factors make it easier to analyse a player’s individual performance looking just at the stats. However the only major consideration that xG does not take into consideration is a goalkeeper mistake so be careful when just purely looking at a player or a team's raw xG data.
A recent game where xG was calculated was Arsenal vs Leeds United where Arsenal won 4-2 despite a late surge from Leeds scoring 2 goals in the second half.
The xG for this game was, Arsenal- 2.34 to Leeds- 1.06. In the first half alone Arsenal created a xG of 1.75 and Leeds just a mere 0.15. This shows the football fans that Arsenal's attacking play was better than the stats show.
Recruitment is a HUGE factor in modern day football even more so in the premier league where big marquee signings are expected to hit the ground running. For example, this season Chelsea's new summer signing Timo Werner who last season for RB Leipzig averaged 0.75 xG per game however this season he is only averaging 0.50. This means he is getting into scoring positions less frequently and therefore not having the same impact in the game and this is part of a reason why he is being considered a “flop” so early on.
A player whos xG is very good however is Ivan Toney of Brentford who is rumoured to be a West Ham target in the summer. He is currently on 17.78 xG in 29 games, however he has scored 23 goals which means he is scoring from harder shots and he is scoring when the statistics say he shouldn't. This is a sign of a clinical finisher.
xG is also closely linked to another important stat that is “expected points”.
If the premier league table was based on how many expected points a team has, which correlates to a team’s xG for and xG against, there would be some significant changes to the table. For example, 7th place Everton are expected to have 27 points based on xG but they currently sit on 37. This would make a lot of difference as they would find themselves in 13th place.
On the other end of the spectrum, Brighton sit in 15th place having only 26 points and only scored 25. The expected goal stat says they should have scored 35 goals and they should have 13 more points and sit on 38 which would put them 6th in the table.
In a league where the finest of margins mean so much to each team's title charge and survival fight, xG can help EVERY team achieve success.
Written By Mac Egan