This was originally published in the Sep 21st edition of Expected Goals, my daily newsletter. If you want 5-10 minutes of team and player analysis in your inbox every morning, sign up here.
The
Penn Quakers defensive unit has shown a remarkable performance in the 2023 season. The Quakers defense stood tall, ranking 11th nationally after adjusting for the strength of the opposing offenses, landing them in the 78th percentile. (Their raw numbers may not look as impressive, as their efficiency was perfectly average - 50th percentile - if you don't adjust for the strength of their opponents.) The standout skill for the Penn defense was their on-goal shooting percentage, which ranked in the 90th percentile nationally, thereby restricting their opponents to an on-goal shooting percentage of 41.8%. On-goal shooting percentage is goals divided by shots-on-cage, so it is focused on high-leverage situations that are either goals or saves. Their shooting efficiency allowed, which is a better version of shooting percentage, also ended up in the 90th percentile.
Their season had its peaks and valleys. A notable 4-game stretch from March 4 to March 18 marked their best defensive performance, with an adjusted defensive efficiency of 22%, which is the equivalent of a top-5 defenses if extrapolated out over a full season. During this period, they bested Saint Joseph's and Princeton, and fell to Penn State and Villanova. Given the strong defensive play, it's reasonable to put those 2 losses on the other units. In contrast, the worst stretch took place between March 26 and April 15 with an adjusted defensive efficiency of 33% (equivalent to the 60th ranked defense). They still managed victories against Yale and Harvard, yet suffered defeats at the hands of Cornell and Brown. The differences in these periods were stark. The on-goal shooting percentage allowed increased from a solid 40% during the good stretch to a not-so-good 51% during their worst.
When we zoom out and look at the 12 games they played against conference opponents or similarly ranked LaxElo teams, the picture gets clarified a bit. In the 8 games where the opposing offense had a shot-on-goal rate of over 64.2%, Penn's record was 3-5. Conversely, with a shot-on-goal rate of less than 64.2%, Penn went 3-1. It suggests that Penn's defense was markedly more successful when the opposing team had fewer shots reaching the goal. I always equate a higher shot-on-goal rate with an offense that is comfortable. The metric cited above, on-goal shooting percentage, can be the result of a goalie not seeing the ball and not making saves OR a defense that is giving up higher quality shots. When we see that shot-on-goal rate is the more important split, that suggests that when they struggled, it was more about the defense allowing a higher quality shot, on average.
Taking it a slightly different direction, the duration of opposing possessions also played a significant role in the Quakers' defensive outcomes. Their best performances were observed in possessions lasting 40-59 seconds, where they allowed goals on only 28.2% of possessions, 4.9 percentage points better than the average. Meanwhile, quick possessions of 0-19 seconds proved challenging, with goals allowed on 29.4% of possessions, 4.2 percentage points worse than the average. This indicates that the Quakers defense was more vulnerable early in the shot clock and transition defense is the biggest area for improvement. If they could get to the later stages of the possession, the defense was much much more effective.
While the Quakers struggled against teams with high shot-on-goal rates, their overall defensive strength was undeniable, as shown by the #17 final ranking. But as interesting as their defensive trends are, it seems like the play of the defense was more consistent than the offense and their play between the boxes.
