Fastball Velocity Increases: Effects on Performance and DL Time

Every season starts with stories of how pitchers are losing fastball velocity. While pitchers that lose velocity fill the headlines, a few actually see a velocity spike. A velocity spike is great for a pitcher because it usually means better performance and less time on the DL during that season.

Bill Petti and I have been beating to death the aging curves of pitchers as seen here and here and even here. Well, it is time to keep beating this dead horse. Here is the aging curve for pitchers that saw a 0.5 MPH or great increase in their fastball velocity:

A velocity increase generally means two things for a pitcher’s production. Before the age of 30, the pitcher will likely see increase performance. After 30, they will just maintain their output. One of the biggest keys for me taken from this graph is the constantly increasing BABIP line. In all the aging curves, the BABIP line never goes down, just up. I have a feeling that hitters gain the advantage over pitchers as they become more and more familiar with each other.

Not all pitchers see an improvement in their stats because of an increase in fastball velocity. The odds of an improvement increase significantly if the spike in velocity is 1 or more MPH. I looked at all, starting, and relief pitchers and here is the percentage chance of each stat improving given a velocity increase:

Not surprisingly, a pitcher’s K rate is most likely to improve with an increase in velocity. Another key data point is BABIP. Again, it just stays the same for the increase in velocity. The aging data for batted balls, BABIP and HR/9, are fairly independent of velocity.

Finally the most surprising find, to me anyway, is that an increase in velocity means the pitcher has a significantly less chance of ending up on the DL that year. To get the data, I took all pitchers that threw 120 IP in year 1, were mainly a starters in year 2 (more starting IP than relief IP) and increased their velocity by 1 MPH or more in year 2. I had to use this subset of pitchers so I would have a baseline of data available. Normally, 39% of these pitchers will end up on the DL in any given season. Of the 59 pitchers that saw the large bump in velocity, only 8 went on the DL the next year -or- 14%. A starting pitcher that sees an increase in his fastball by 1 MPH, is 2.8 times less likely to end up on the DL that season. Increase performance and less DL time, sign me up.

There could be a couple of reason for the pitchers seeing less time on the DL. The pitcher could be healthy in the 2nd year and therefore throwing harder. Also, the pitcher won’t have to go on the DL because they suck they have some mystery illness.

Here are the starting pitchers that are seeing an increase in velocity from 2011 to 2012 along with some of their stats (blue = better stats, red = worse stats):

Pitchers experiencing a velocity increase should expect better results on the mound. Another side benefit is that the pitcher is less likely to go onto the DL. While pitchers seeing a velocity increase are fairly rare, they should be targeted for fantasy teams.