It may seem that fastball velocity gets over utilized for explaining a pitcher performance, but I don’t think it gets used enough. As I get going full steam ahead in my off-season research, I find myself always looking to see how a pitcher’s velocity held up over the season. Instead of looking up each pitcher individually, I decided to go ahead and collect 2018 fastball velocity reading for an easy reference.
For the data, I found the pitcher’s velocity for the whole season, April to June, July to October, and just September/October. The entire data dataset can be found here.
I went through the data and found some intriguing pitchers who gained and lost a few ticks. I divided up the analysis between first versus second half and first half and September. Many of the same pitchers would have made both lists. Here is the first to second half values.
Notable 1H to 2H Fastball Velocity Changes
Stephen Strasburg is the most concerning name on the list with his fastball down ~2 mph. The drop occurred after he went on the DL with shoulder inflammation.
His results also took a hit with his ERA going from 3.46 to 4.20 and his K%-BB% dropping from 23% to 19%.
Strasburg is getting in the danger zone where his fastball will start losing its effectiveness if he loses any more velocity. Here are its swinging-strike rates since he joined the league at different velocities.
Strasburg’s Fastball Swinging-Strike Rate
| mph |
SwStr% |
| 92 |
4.8% |
| 93 |
7.0% |
| 94 |
12.7% |
| 95 |
13.9% |
| 96 |
16.8% |
| 97 |
14.7% |
| 98 |
16.0% |
The fastball starts to lose its effectiveness as it dips near 93 mph.
With the velocity drop, Strasburg will still be a good pitcher because his changeup is elite and curve and slider are decent. His issue is that he’s already been cutting his fastball usage from 73% when he entered the league to 52% last season. I think the chances of him having that elite season has passed.
One major consideration will be if he can get his walks under control. In the first half, they were at 2.1 BB/9 but jumped to 3.5 BB/9 in the second half. Spring training reports are going to matter quite a bit on how he gets valued.
Notable 1H to September Fastball Velocity Changes
Corey Kluber is the name which jumps off. For pitcher going in the second round of mock drafts, an ~1.5 mph drop in his fastball throws a major red flag.
He got hit around more in the second half with his BABIP jumping from .248 to .321 while list strikeout and walk rates remained constant (22.5 K%-BB% to 22.1 K%-BB%). Kluber found a way to be effective even with the velocity loss.
My gut says something is off but I can’t find it. His steamer projection has his ERA next season back in the 3.50 range (same as 2015). so it even sees that something is not right. I’ll read some more previews as the season nears and see if I can gain a better understanding of him.
