Did Trevor Bauer Discover a Road Map to Another Level?

This past Tuesday night against Oakland — just as there have been at other times this season — Trevor Bauer showed glimpses of the bat-missing strikeout artist he can be, the top-of-the rotation potential he’s possessed since departing UCLA with Tim Lincecum-like Pac-12 numbers and starter-kit stuff.

Bauer set a career high with 14 strikeouts against the A’s on Tuesday, and he has a career-high strikeout percentage (29.2%) and strikeout-walk rate differential (22.1 points) this season — nearly doubling his career rate (12.4-point K-BB%) by that measure.

Having spent some time around him this year, I’ve learned that Bauer believes he’s making improvements, is changing for the better on a skill level — in part evidenced by his strikeout rate. He’s been frustrated by the results (6.00 ERA), but believes they aren’t reflective of a sound process. That idea is supported by a 3.98 FIP.

Besides the strikeouts, what also stood out on Tuesday night was Bauer’s curveball usage. Bauer recorded a career-high single-game total of curveballs (47) and a career-high curveball percentage (40.7%) against the A’s. On the season, he’s throwing the pitch at a career-high rate of 24.6%. The pitch has helped him increase his strikeout rate even while his overall swinging-strike rate has remained flat at 9.0% this season. Bauer has enjoyed 58 called strikes via his curveball this season, compared to 95 all of last year.

Said Bauer, after the game, to reporters regarding curveball:

“I mean, it is my best pitch,” Bauer said. “It always has been. So, when it is working, it is nice. When it is really good, like tonight. I just try to leverage it and use it as much as possible.”

The pitch is also a swing-and-miss weapon. Consider some evidence from Tuesday night, like when he struck out the side with the pitch in the fifth inning:

It can work against lefties, too:

Nearly a third of the time hitters offer at the pitch, it creates a whiff. Consider this feeble swing from Adam Rosales:

And while Bauer has league-average fastball spin rate, he does have enough velocity to change eye levels and work up to play off the curveball. Here’s a 97 mph fastball up for a whiff:

Bauer’s final at-bat, and strikeout, ended with a filthy biting curve:

Bauer was pumped.

After Bauer recorded seven strikeouts with the pitch Tuesday, batters have now posted a .103 isolated slugging mark against the curve this season and an .081 mark for his career — the lowest rates among his pitches. Perhaps he should be leaning on the pitch more often. Of the six different ones he throws, the curveball is the only pitch with a positive linear weight for his career (16.6 runs above average) and has been his most effective pitch this season (1.4).

Among pitchers who have thrown at least 100 curveballs this season, Bauer’s ranks second in vertical break, according to Baseball Prospectus.

Perhaps Bauer is an ideal candidate to join the curveball renaissance, which has been led by pitchers like Rich Hill, Lance McCullers and Drew Pomeranz. They’re pitchers who have dramatically increased usage of the pitch and have been better able to prevent runs.

Bauer prides himself on having a versatile pitch mix. He feels it gives him options to adjust and attack hitters in a variety of ways. Perhaps he would be better served by simplifying his mix and becoming more curveball dependent.

There’s a perception that the cerebral and unorthodox Bauer is stubborn. Indians coaches have expressed an interest in Bauer simplifying his approach. Said Indians pitching coach Mickey Callaway to The Athletic’s T.J. Zuppe on Bauer’s troubles earlier this season: “I think he needs to simplify the mix again, once again.”

But Bauer is curious. He was interested in pitch tunneling, he’s as data-savvy as any pitcher. He seems like an ideal candidate to experiment with more reliance on spin and reduce his four-seam usage, a pitch he’s throwing at a 55.1% rate this season, above his 52% career average.

On Tuesday, Bauer said the curveball was working, hence the usage rate. Perhaps he felt he had a better feel for it than most games. According to PITCHf/x, however, neither the horizontal nor vertical movement were season bests.

Here’s Bauer’s vertical movement by start:

And the horizontal movement by start:

According to PITCHf/x data, Tuesday was not an outlier for the pitcher’s usage and effectiveness.

The curveball trend became a thing last season. Spin is king. Others arms, like Hill, McCullers and Pomeranz, are using their hooks to reach new levels of performance. And perhaps it is a road map for Bauer to follow to reach his next level of performance, to fulfill his promise.

Perhaps it is the curveball that could give the Indians’ staff another legit top-of-the rotation for the second half of the season, and perhaps another asset for a lengthy run of October baseball. Bauer is still just 26. He could still very well be evolving.