I can’t believe I burned that headline on what’s going to be such a modest batch of information, but I can believe that Spencer Turnbull has found his way to the top of the Detroit Tigers rotation this year. I don’t think any serious baseball fan still thinks about pitcher wins and losses anymore, but Turnbull obviously was much better than his 3-17 “record” in 2019. 

The exciting news is that he’s been even better than expected so far in 2020. With a 2.78 ERA/2.85 FIP, he’s the best Detroit pitcher by fWAR (0.7) and bWAR (0.6).

MLive Tigers beat reporter Evan Woodbery noted this morning that Turnbull’s likely to regress as the season proceeds, and he’s right: there are some signs pointing in that direction. Woodbery points to SIERA, an ERA estimator, which sees Turnbull as about two runs worse than his current ERA. To that I would add Turnbull’s .283 batting average on balls in play, which is about fifty points lower than his 2019 BABIP and seems likely to increase. His DRA, 3.56, also pegs him as a little worse than his ERA and FIP suggest, though still clearly the best among the current rotation.

There also are signs these good results might stick, though. Here’s a FanGraphs/RotoGraphs report from yesterday, which highlights Turnbull alongside Trevor Bauer as two pitchers who have produced significantly increased movement on one of their featured pitches. For Turnbull, it’s his slider, which has been his main out pitch:

Last year Turnbull’s main strikeout pitch was his slider which had a 15.3 SwStr%. That isn’t the greatest number to have as your main swing and miss pitch. He already has a really good four-seam fastball so pairing it with a true swing and miss pitch was the key to Turnbull having a better 2020 season. So far this season Turnbull’s slider has a 26.5 SwStr%. It also has a higher O-Swing%, better wOBA against, and better ISO against. But again, small sample size so we have to look deeper to make sure this is indeed legit.

To start, Turnbull increased his sliders RPMs. It has gone from 2,438 RPMs in 2019 to 2,533 RPMs this season thus resulting in more movement. His slider movement went from having an overall movement of 3.3 inches to 3.9. He did this mainly by increasing its horizontal movement. Something he seems to be working on in the past three years. Its movement in inches starting in 2018 went from 2.29 to 3.07 and now to 3.51. 

The increases in spin rate and movement on his slider show that Turnbull still is developing, refining, and improving his arsenal, and they constitute evidence that he may be ready to outdo the performance levels his past baselines suggest.

One other thing I’ve been wanting to document this year is the way Turnbull mixes speeds. The graph below plots the velocity of every pitch he threw in his first start of the 2020 regular season. In five complete innings, he only allowed three hits (just ten total balls in play) and recorded eight strikeouts, and it was clear that he had the Cincinnati batters off balance all day. This yo-yo velocity chart is a big part of the reason why.

Of course, Turnbull’s stay atop the Detroit rotation might not last long. Focusing on the positives in that regard, ostensible number one Matthew Boyd could recall the location of home plate at any moment. Even more exciting possibilities are the arrivals this week of highly anticipated pitching prospects Tarik Skubal and Casey Mize. Skubal is scheduled to make his first major-league start tonight, followed by Mize’s debut tomorrow night. Could we be witnessing the emergence of a 2013-era rotation in the Motor City? That’s an extremely high bar, but there’s no reason not to permit yourself a little bit of excitement during these rebuilding times.

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Previously
RKB: 2020 Detroit Tigers Season Preview – UPDATED PECOTA Ed.
RKB: 2020 Detroit Tigers Season Preview – Spring Training Ed.
RKB: 2020 Detroit Tigers Season Preview – Payroll Ed.
RKB: 2020 Detroit Tigers Season Preview – PECOTA Ed.
RKB: How does new Detroit Tiger Austin Romine relate to his teammates?

Related
Breakout prospect Tarik Skubal earns his first shot at the majors – Bless You Boys
The Call-Up: Tarik Skubal – Baseball Prospectus
The Call-Up: Isaac Paredes – Baseball Prospectus
Meet Isaac Paredes, the 21-year-old who is patient, punctual and experienced beyond his years – MLive