In American football, a pass rush is an attempt by the defensive team to disrupt the offense and prevent the quarterback (QB) from completing a pass. Existing metrics for assessing pass rush performance are either discrete-time quantities or based on subjective judgment. Using player tracking data, we propose STRAIN, a novel metric for evaluating pass rushers in the National Football League (NFL) at the continuous-time within-play level. Inspired by the concept of strain rate in materials science, STRAIN is a simple and interpretable means for measuring defensive pressure in football. It is a directly-observed statistic as a function of two features: the distance between the pass rusher and QB, and the rate at which this distance is being reduced. Our metric possesses great predictability of pressure and stability over time. We also fit a multilevel model for STRAIN to understand the defensive pressure contribution of every pass rusher at the play-level. We apply our approach to NFL data and present results for the first eight weeks of the 2021 regular season. In particular, we provide comparisons of STRAIN for different defensive positions and play outcomes, and rankings of the NFL's best pass rushers according to our metric.

翻译：在美国橄榄球中，防守冲传是防守方试图破坏进攻、阻止四分卫完成传球的战术。现有评估冲传表现的指标要么是离散时间统计量，要么基于主观判断。本文利用球员追踪数据提出STRAIN——一项用于评估美国国家橄榄球联盟（NFL）冲传球员的新指标，可在连续时间维度进行单次攻防分析。受材料科学中应变率概念的启发，STRAIN是一种简单且可解释的衡量橄榄球防守压迫力的方法。该指标是直接观测统计量，由两个特征构成：冲传球员与四分卫之间的距离，以及该距离缩减的速率。我们的指标对压迫力具有出色的可预测性，且随时间保持稳定。我们还拟合了STRAIN的多层次模型，以理解每位冲传球员在单次攻防中的防守压迫贡献。我们将该方法应用于NFL数据，并呈现2021赛季前八周的分析结果。具体而言，我们比较了不同防守位置与攻防结果下的STRAIN值，并根据该指标对NFL最佳冲传球员进行排名。