Alex MacQuoid
xG’s Inconsistencies in the Premier League
Last weekend’s Premier League results highlighted the discrepancies between expected goals (xG) and actual outcomes. In 10 matches, xG aligned with the result in only three fixtures. Manchester United (2.27) lost 1-0 at home to Everton (0.16), a result xG couldn’t account for due to Everton’s red card and defensive resilience.
Despite these inconsistencies, xG remains a valuable metric. In week 11, it matched seven results, and in week 10, it had eight correct. Since 2021-22, xG has an accuracy level of 59%, and this season, it’s at 57.5%.
xG as a Long-Term Metric
xG isn’t designed to predict individual match outcomes but to assess a team’s chance creation and conversion effectiveness over time. For instance, Aston Villa, Sunderland, and Tottenham would be in the bottom four based on xG, but their actual goal tallies place them higher.
Villa’s success from distance and excellent goalkeeping from Robin Roefs and Guglielmo Vicario skew xG’s predictive power. As one analyst noted,
If you leave a game saying ‘I can’t believe we lost that,’ you likely had a higher xG than your goal return.
Tactical Trends Influencing xG
Several tactical trends this season impact xG’s accuracy. Teams are increasingly exploiting set-pieces, where choreographed routines lead to higher goal conversion rates than xG models predict. Opta’s xG model, which considers factors like shot distance and pressure, often underestimates the effectiveness of well-worked set-pieces.
Another trend is attacking deep-defending teams. Spurs and Villa have scored frequently from low xG chances by pushing defenses back and creating unopposed shots. Additionally, teams with strong free-kick takers, like Villa, often overperform their xG from set-pieces.
Villa’s 4-0 Win Against Bournemouth
Villa’s 4-0 victory over Bournemouth illustrated these trends. Despite scoring four goals, Villa’s xG was just 1.88, lower than Bournemouth’s 2.01. Villa’s goals came from low xG shots, including a 0.14 xG free-kick by Emiliano Buendia and a 0.04 xG shot by Amadou Onana.
The Bigger Picture
While xG may not tell the whole story for individual games, it tends to even out over a season. Last season, the four teams with the highest xG wins finished in the top five. However, tactical trends and individual quality can skew xG in the short term.
The beauty of football lies in its unpredictability, and xG isn’t trying to change that. It’s a tool to assess performance over time, not to predict every match outcome.
Read also: Mbappé’s Nine Goals in Five Games: A Historic Champions League Feat