Xander Bogaerts' put the Red Sox ahead for good on Tuesday night against the Marlins with a three-run single in the seventh inning. The radar gun said it was a 99 mile per hour fastball -- plenty fast already! -- but as Ian Browne of MLB.com points out, Bogaerts was seeing velocity much faster than even that.
You see, Marlins' pitcher Carter Capps has a very strange delivery, one that sees him hop forward off the mound before releasing the ball. He's also 6-foot-5, so he already had some serious extension on his release, and the combination of those two things gives him a much higher perceived velocity than his actual velocity. In the case of the pitch Bogaerts' smacked into right for a bases-clearing single, we're talking 105.5 mph.
This data is available to us thanks to MLB's Statcast, which tracked Capps' pitch as having the highest perceived velocity of any thrown this season -- not just by Capps, but by anyone. This is thanks to the 9.5 foot extension Capps got off of the mound. Yes, 9.5 feet of extension. It makes sense, when you consider he jumped in front of the mound before delivering, and that the wingspan of a 6-foot-5 pitcher makes up the rest of the distance as he moves towards the plate while releasing the ball.
Perceived velocity isn't a new idea, by any means. Randy Johnson was so difficult to hit not just because he threw hard, but because it looked even faster than it registered on the radar gun thanks to his being 6-foot-10. It's also been a huge help to Chris Young, a 6-foot-10 pitcher who throws in the high-80s, as his perceived velocity was (and still is) in the 90s thanks to his long arms and delivery. These days, though, perceived velocity can be tracked easily, since Statcast seems to be doing its best to track just about everything, meaning we get to see moments like this one in the light they deserve.