Trevor Williams was on quite a heater in the second half of the season. Not because of his actual heater, mind you, which is below-average by today’s standards at 90.5 mph (18th percentile in MLB).
No, Williams was on the proverbial ‘amazing luck’ heater. Starting on July 11th and continuing through to the end of the season, Williams pitched 76.2 innings and allowed only 11 earned runs, good for a deadball era-esque 1.29 ERA. While facing 307 batters during this stretch, Williams issued 23 walks ( 7.4 BB%) and struck out 58 (18.9 K%).
Both his BB% and K% marks during this stretch were relatively in line with his overall marks of 18% and 7.9% for the season, which accounts for his not-so-great first half that resulted in a 4.60 ERA. So how did he do it?
It would be easy to just attribute it to smoke and mirrors, which is something that I was personally guilty of doing at times. But Williams may have a skill that doesn’t need velocity from his arm to obtain. By digging into Statcast, Williams became a master at suppressing exit velocity. Here’s a look at his exit velocities by pitch type over 2018.
If you click the Statcast link above and do the Baseball Savant hoodoo, you can see this interactively. If you’re relying on me to be your tour guide, let me draw your attention to the fact that three of Williams’ four pitches all dropped by exit velocity after July: sinker, slider, and changeup.
The sinker dropped from 91.1 EV to 87.9 EV from July through September; the slider went from 83.2 to 80.8; the changeup went from 84.4 to 78.2. For the year, Williams placed in the 90th percentile for exit velocity in all of MLB.
Williams isn’t doing this because of exceptional spin on his pitches, like the Astros seem to have unlocked with their staff, as his fastball spin is in the 20th percentile and the curve just a measly 4th percentile.
He just put the ball in locations that were difficult for batters to do damage on it. Is this a repeatable, sustainable skill from season to season?
The Steamer and ZIPS projection systems (which I personally don’t put a lot of stock into) don’t have a lot of faith in Williams this year. Steamer has him making just 26 starts and pitching 145 innings, with a projected 4.72 ERA/4.50 FIP, good for just a 1.1 fWAR. ZIPS is only slightly more optimistic — 28 starts and 155 innings, putting up a 4.06 ERA/4.18 FIP in the process for a 1.7 fWAR.
Now, I’m not the world’s biggest Williams fan, but he’s not going to be that bad. In his first two seasons as a starter, he’s posted 2.2 and 2.5 fWAR. That’s a #3 to #4-level starter. And if this exit velocity suppression is actually a thing, then his low K% is going to also suppress how well WAR is going to view him. I think he’s good for 180-190 innings and should be in the high 2 WAR range.
Williams isn’t as bad as his 4.60 ERA through the first 19 games and not as good as the 1.29 ERA in his last 13 starts. He finished at 3.11 ERA and 3.86 FIP, again because of his K rate.
If Williams lands somewhere around a 3.75 ERA/4.00 FIP range with the aforementioned inning total, that’s a solid #3 starter, which is realistically what his ceiling is. As amazing as it was to watch Trevor Williams remind everyone of 1968 Bob Gibson in the second half last year, it’s just not realistic.
It’s also not realistic to automatically assume he’s going to regress so badly that he’s a #5 starter. I’m guilty last year of comparing him to a Jeff Karstens 2.0 — a guy who operated with a sub-standard fastball, too. Karstens, and now Williams, have less margin for error than a guy with better ‘stuff’.
After reviewing the data, I’m confident that Williams is a better long-term proposition than Karstens. Williams is pretty good. And that’s OK.