When to Believe Velocity Gain
Last week, I wrote about some findings regarding in-season fastball velocity loss and how experiencing a loss in different months affects a pitcher’s chances of finishing a season with diminished pitch speed. The general takeaway was that June and July were the most telling months.
But what about velocity gain? We know that, generally speaking, pitchers lose velocity more than they gain it. So while velocity loss isn’t good, it’s to be expected — and starting pitchers seem to be able to deal with that loss better than relievers. Pitchers who can stave off velocity loss (year-over-year change between +/- .5 mph) perform even better. Moreover, if a pitcher gains at least 1 mph on their fastball in a season they are twice as likely to maintain some or all of that gain the following year.
Gaining velocity, while not a guarantee of better performance, is certainly a boon to a pitcher and his organization. But given that velocity varies for all sorts of reasons, when can a team have confidence that the increase they’re seeing is real and sustainable?