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xG (Expected Goals) is an increasingly popular statistic in football to measure the quality of chances a team creates in a game. Our experts have also put together a fantastic guide on xG in football which you can read first, to get an understanding of this statistic before diving into NPxG.
Alongside the more commonly used xG, and xGF/xGA (expected goals for and against), you may also have seen mention of NPxG (Non-Penalty Expected Goals). This article will break down what Non-Penalty xG is and how to use Non-Penalty xG Ratio to your advantage when betting on football.
🤔 What is NPxG (Non-Penalty Expected Goals)?
Non-Penalty Expected Goals (NPxG) is a variation of the standard Expected Goals (xG) metric that measures the likelihood of a shot resulting in a goal but excludes penalties. It provides a more accurate assessment of a player or team’s scoring potential from open play or set pieces like corners and free kicks, without the distortion caused by penalty shots.
Penalties typically have a much higher xG value (around 0.75–0.80), making them far more likely to result in a goal than shots taken in other game situations. Therefore, NPxG helps isolate the ability of a team or player to create scoring chances without the aid of these high-probability penalty kicks.
By focusing on open play and set-piece situations, NPxG offers a clearer picture of how effectively a team generates quality chances and creates an understanding of their attacking strength. Since penalties represent a significantly different challenge compared to shots taken in open play, excluding them gives a more nuanced understanding of scoring opportunities and team or player efficiency.
📈 What is Non-Penalty xG Ratio?
Non-penalty xG ratio is a metric used to measure the proportion of a team or player’s total xG that comes from non-penalty situations. This ratio helps differentiate between players or teams who rely heavily on penalties and those who generate high-quality chances through open play or set pieces. A high non-penalty xG ratio means that the team or player is creating chances that come from open-play scenarios, demonstrating more reliable scoring potential.
A ratio is a relationship between two things when it is expressed in numbers or amounts. For example, using xG. Team A has an xG of 2.14 and Team B has 1.12. The total xG in that match is 3.26 of which Team A contributed 0.656 or 65%. The greater the ratio the better that team has performed. In the above example, Team B would have a ratio of 34%. You can build this information over several games and the teams who have the greater xG ratio are those that are often generating higher xG than their opponents.
The table below is from the 2023/24 season, and we can see that Arsenal had the best NPxG ratio. Arsenal games averaged 2.19 xG per game of which the Gunners contributed 1.61 or 73.5%. Whereas Sheffield Utd had an NPxG ratio of just 32.6%.
We can see that Man United, despite finishing eighth in the League, would have finished 15th on NPxG ratio, meaning according to this metric, they were lucky to finish as high in the table as they did. Whilst the 2024/25 season is still very early, should we be surprised that Wolves are struggling given that they have the fourth worst NPxG ratio after the three relegated sides last season?
🔬 How is Non-Penalty xG calculated?
Non-penalty xG is calculated by assigning a value between 0 and 1 to each shot based on several factors that affect the likelihood of a goal. These include:
- Shot Location: Shots taken closer to the goal are more likely to result in goals.
- Shot Angle: Shots from narrow angles have a lower probability of scoring.
- Type of Shot: Headers, volleys, and other shot types are weighted based on historical success rates.
- Body Part Used: Whether the shot was taken with a foot or head can impact the xG value.
- Defensive Pressure: How tightly marked the shooter was and the positioning of defenders or the goalkeeper at the moment of the shot also factor in.
These factors are based on historical data from thousands of shots with similar characteristics, allowing the xG model to assign a probability of the shot resulting in a goal.
📋 How Do We Understand Non-Penalty xG?
Non-penalty xG provides deeper insight into a team’s or player’s effectiveness in open play and set pieces by filtering out the inflated goal probability of penalties. It reveals:
- True Offensive Capability: NPxG allows analysts to see how well a team creates quality chances without the distortion of penalty shots, giving a better sense of a team’s offensive performance.
- Player Efficiency: For players, NPxG helps distinguish between those who rely on penalties to boost their goal tally and those who are consistently generating quality chances in regular play.
- Predictive Power: NPxG helps predict future performance more reliably than standard xG, especially when penalties skew the total xG value.
In essence, non-penalty xG is used to isolate and evaluate the chances created or conceded in open play, offering a clearer picture of both offensive and defensive performance.
✅ What Are the Benefits of Using Non-Penalty xG Ratio When Betting?
Using non-penalty xG ratio in betting strategies can provide significant advantages:
- Better Performance Insight: NPxG ratio helps bettors evaluate a team’s or player’s true attacking performance without being misled by penalties, which are not always a reliable or repeatable aspect of a game.
- More Accurate Predictions: By focusing on NPxG, bettors can identify teams that consistently create high-quality chances, which can help in making more informed decisions in markets like over/under goals or player-specific bets.
- Long-Term Consistency: Since NPxG focuses on open play, it provides a more sustainable and reliable metric for assessing teams or players across an entire season, where the number of penalties taken can vary widely.
For example, if a team has a strong non-penalty xG but has been scoring fewer goals than their NPxG suggests, it might be worth betting that they will eventually outperform their previous results, as their chances created indicate better long-term potential.
⛔️ What Are the Negatives of Using Non-Penalty xG Ratio When Betting?
While non-penalty xG ratio offers many advantages, there are also some limitations to consider:
- Penalties Still Impact Matches: Excluding penalties entirely from analysis can sometimes give an incomplete picture, especially for teams or players who are strong at winning and converting penalties.
- Limited Context: Like all xG models, NPxG doesn’t account for factors like the quality of the opposition’s defence, shot power, or goalkeeper positioning. These factors can influence the real-world outcome of shots more than an xG model might predict.
- Short-Term Variance: Football is a low-scoring sport, meaning that variance can heavily influence the results of a few games. A team might create high-quality chances (as indicated by NPxG) but still underperform in actual goals for several games due to random events like poor finishing or excellent goalkeeping.
- Reliability on Historical Data: NPxG is based on historical averages, which may not always capture unique game situations or exceptional performances that fall outside typical patterns.
Despite these downsides, non-penalty xG remains a valuable tool in providing deeper insights into team and player performance. For betting purposes, it’s best used alongside other metrics and observations to craft a comprehensive strategy.
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