Summary: The two main explanations currently offered for the MLB home run record of 2017 are suspected changes in the manufacturing of the baseball and the new approach by hitters with increased launch angle and exit velocity. But what about the pitchers? Was there a change in pitch quality? Our Quality of Pitch (QOPTM) statistic declined across all pitch types in 2017. We show that the drop in QOPTM average can be traced primarily to a change in two key components: vertical break and horizontal break. It is shown that the switch from SportsVision cameras to the Trackman doppler radar-camera data collection system is not sufficient to explain these changes. We conclude that the change in vertical break and horizontal break is a significant factor in explaining the record number of home runs being allowed by MLB pitchers in 2017.
Pitching (Baseball); MLB; Home runs (Baseball)
Wilson, Jason and Wong, Jordan T., "Explaining the MLB Home Run Record of 2017 with Quality of Pitch (QOPTM)" (2018). Faculty Articles & Research. 391.