The plus/minus rating is one of the most widely recognized statistics in NHL analytics, often cited by coaches, commentators, and fans alike. While it appears straightforward at first glance, understanding the nuances of the plus/minus rating can provide deeper insights into a player's defensive and offensive impact on the ice. In this article, we’ll explore what the plus/minus rating measures, how it is calculated, its limitations, and its relevance in modern hockey analytics.

What is the Plus/Minus Rating?

The plus/minus rating is a statistic used to evaluate a player's impact on team scoring during even-strength or shorthanded situations. Essentially, it measures the goal differential when a player is on the ice. A player receives a “plus” (+1) each time their team scores an even-strength or shorthanded goal while they are on the ice, and a “minus” (−1) each time the opposing team scores under the same conditions.

For example, if a player is on the ice for 30 goals scored by their team and 20 goals scored by the opposition at even strength or shorthanded, their plus/minus rating would be +10.

How is the Plus/Minus Rating Calculated?

The calculation is straightforward but excludes certain types of goals to ensure the rating reflects a player's impact during normal gameplay situations:

  • Plus (+1) when the player is on the ice and their team scores an even-strength or shorthanded goal.
  • Minus (−1) when the player is on the ice and the opposing team scores an even-strength or shorthanded goal.
  • No change for power-play goals scored by the player's team or the opposing team while the player is on the ice.

Power-play goals are excluded because being on the ice during a man advantage or disadvantage inherently skews the likelihood of goals for or against, which could distort the player's actual defensive or offensive contributions.

Interpreting Plus/Minus Ratings

A positive plus/minus rating suggests a player is on the ice for more goals scored by their team than goals scored against, which can indicate strong defensive play combined with offensive support. Conversely, a negative rating may imply the player is often on the ice when the opposition scores, potentially signaling defensive weaknesses or poor team performance during their shifts.

However, it is critical to consider the context of the player’s role and the team’s overall performance when interpreting this stat. For example, players who regularly face the opponent’s top lines or defensive specialists may have lower plus/minus ratings despite strong individual play.

Limitations of Plus/Minus Ratings

While plus/minus offers valuable information, it has some notable limitations that analysts and fans should be aware of:

  • Team Dependency: Plus/minus can be heavily influenced by the overall strength and style of the player's team. Players on strong, high-scoring teams tend to have better ratings regardless of their individual play.
  • Context Ignorance: The statistic does not account for quality of competition, zone starts, or individual contributions to goals and goals against.
  • Excludes Special Teams Impact: It ignores power-play goals for and against, which can be significant in evaluating a player's full impact.
  • Situational Variance: Players deployed in defensive roles against top opposition may have lower plus/minus ratings despite effective defensive performance.

For these reasons, plus/minus should not be used in isolation but rather alongside other metrics and qualitative analysis.

Modern Alternatives and Complementary Metrics

As NHL analytics have grown, several advanced metrics have been developed to address the shortcomings of plus/minus. Some popular alternatives and complementary stats include:

  • Corsi and Fenwick: These metrics measure shot attempt differential (Corsi) and unblocked shot attempts (Fenwick) while a player is on the ice, serving as proxies for puck possession and territorial advantage.
  • Expected Goals (xG): Expected Goals models estimate the quality of scoring chances a player helps generate or prevent, providing a more nuanced look at offensive and defensive impact.
  • Zone Starts: This tracks how often a player starts shifts in offensive, neutral, or defensive zones, helping contextualize plus/minus and other stats.
  • Relative Metrics: These compare a player's stats to their teammates when the player is off the ice to better isolate individual impact.

By combining plus/minus with these analytics, teams and analysts gain a clearer picture of a player's true value on the ice.

Using Plus/Minus to Evaluate Players

Despite its limitations, plus/minus remains a popular and useful tool when used appropriately. Here are some tips for incorporating plus/minus into player evaluation:

  1. Consider Team Context: Look at the player’s plus/minus relative to their teammates and team performance during the season.
  2. Combine with Qualitative Analysis: Use video review and coaching insight to understand why a player’s plus/minus is high or low.
  3. Integrate Advanced Stats: Use metrics like Corsi, xG, and zone starts to provide context and depth to plus/minus numbers.
  4. Track Over Time: Evaluate trends in plus/minus across multiple seasons rather than isolated snapshots.
  5. Adjust for Role and Usage: Consider the player’s deployment, such as defensive assignments or penalty kill minutes, which impact plus/minus outcomes.

When used thoughtfully, plus/minus ratings can help identify players who consistently contribute to positive play and team success.

Conclusion

The plus/minus rating is a foundational NHL statistic that offers a quick snapshot of a player's impact on the scoreboard during even-strength and shorthanded situations. While it has limitations—especially its sensitivity to team context and situational usage—it remains a valuable piece of the broader analytical puzzle.

As hockey analytics continue to evolve, combining plus/minus with advanced metrics and qualitative insights provides a richer understanding of player performance. By appreciating what the plus/minus rating reveals and where it falls short, fans and analysts can better evaluate the contributions of players on the ice.