In the modern game data is now the centrepiece of football from probability data including expected goals (xG) to real-time tracking of football players available via many betting apps. With football being a game of such high margins, data has changed the way players are viewed especially in the case of attacking players.
Using technology the idea of xG has been formed which by analysing shot distance and angle, among many other conditions can determine the probability of a goal being scored from a specific situation.
A forward that exceeds their xG is a huge benefit to a team, however a forward gathering a lot of xG also suggests that they get into good goalscoring positions – this is seen in Mohamed Salah of Liverpool, who has 3.1 xG this Premier League season but has only scored two goals.
It is important to note that this is a small sample size and so a conclusion cannot be made already; Salah will hope to improve his form when Liverpool plays Chelsea, in terms of Premier League tips this weekend Liverpool are 6/4 favourites to win at Stamford Bridge.
Salah could be vital to Liverpool's Premier League campaign, in general, this season if his ability to get into goalscoring positions is capitalised on, as another thing with xG is that it can be used to compare a player's consistency in front of goal over several seasons.
<blockquote class=”twitter-tweet”><p lang=”zxx” dir=”ltr”><a href=”https://t.co/26Hnbqbee7″>pic.twitter.com/26Hnbqbee7</a></p>— Mohamed Salah (@MoSalah) <a href=”https://twitter.com/MoSalah/status/1567214424825466880?ref_src=twsrc%5Etfw”>September 6, 2022</a></blockquote> <script async src=”https://platform.twitter.com/widgets.js” charset=”utf-8″></script>
The fact Salah regularly performs very closely to his xG in terms of actual goals scored suggests he may be set for a slightly disappointing goalscoring season, although it's early in the season and there is a small sample size.
If Salah were to continue averaging around 0.5 xG per game and scoring around 0.3 actual goals per game he will finish the season with around 19 xG – Salah usually achieves around 20 seasons on the season – and with around 11/12 goals.
A key thing to note with the data is it does not predict the future and cannot be generalised. What the data concludes is that, if Salah were to continue his form in front of the goal in a similar fashion, then he will experience a poor goalscoring season but his xG has not particularly lacked suggesting he is still performing well and getting into good positions.
However, xG changes game by game, especially in the case of top players they will find occasions in which they can comfortably exceed their xG, but this is a huge statistic improbability in terms of maintaining it long term.
The majority of top forwards tend to underperform their xG including Robert Lewandowski long term as they shoot often and so a huge volume of low xG chances that they are unlikely to score accumulate.
— Mohamed Salah (@MoSalah) September 6, 2022
This is why xG should be used as a guide and not to form an entire conclusion, it is useful to demonstrate how well a player positions themselves to receive chances, as well as to indicate an attacker's ability to finish chances in comparison to an average – although to truly indicate ability, a player xG over a long period of time is required.
Another way technology has influenced football is through the implementation of VAR, which also affects attackers as offsides are much more strict often leading to disallowed goals, which can affect strikers' goal tallies.
xG does not take count of offside opportunities and perhaps often a striker could not be lacking goalscoring opportunities but wandering offside too often.