The spin rate on Harvey's average four-seam fastball has taken a similar dip, again in contrast to his peers.
Former Major League pitcher Zach Day, who works at TrackMan, a pitch-tracking system employed by both the Mets and Statcast™, noted that spin rate correlates quite closely with swing-and-miss rate. That, in turn, is an excellent indicator of success -- one way to quantify what pitchers refer to as "stuff," or as Day puts it, "your life on your fastball." So it is worth noting that while Harvey's velocity and spin rate have both fallen, particularly in comparison to the game's other elite starters, his strikeouts have fallen in kind -- from 8.