Velocity, one of the most frequently used tools for evaluating pitchers, represents the maximum speed of a given pitch at any point from its release to the time it crosses home plate. The extent of Velocity's importance has long been debated, but this much isn't: Generally speaking, the faster a fastball is thrown, the harder it is to hit.
Obviously, Velocity is not a one-stop shop for evaluating pitchers. There are pitchers who throw the ball hard who aren't successful because they lack deception, control, movement and reliable offspeed pitches -- among other things. The reverse holds true for pitchers with lower Velocity. They can be very successful by using deception, movement and precision.
Still, the 100 mph fastball is one of the hardest offerings for a hitter to handle. And fans are often transfixed by hurlers who hit triple-digits -- or close to it -- on the radar gun.
Prior to the advent of Statcast, pitch tracking in every MLB stadium was performed by PITCHf/x. One way this system differed from Statcast is that it reported the Velocity of each pitch when it was 50 feet from the back tip of home plate, rather than at the release point. To produce Velocity readings that were closer to pitchers' actual release points, some entities began using 55 feet as the point of reference, inferring what the velocity would be at 55 feet based on the PITCHf/x data for the reported velocity at 50 feet.
Conversely, Statcast can provide the maximum speed of a pitch at any point in its flight -- with the max speed always being at the release point, due to physics -- which allows for a more precise measurement of pitch velocity.
Watch: Statcast tracks Aroldis Chapman's Velocity on a strikeout to end the 2017 AL Wild Card Game.
Achieving high pitch Velocities (especially on fastballs) is skill-based and therefore considered at least somewhat predictive of future performance. If a pitcher is struggling statistically but registering impressive Velocity readings, he may be a candidate to bounce back in the near future. But on a related note, a drop in Velocity could be a sign of pitcher injury. The same exercise can be done with pitchers who are exceeding expectations; if a pitcher is thriving uncharacteristically the presence or absence of Velocity changes may indicate whether he is likely to maintain his performance level on the mound.
In A Call
"pitch speed," "velo," "mph"