Tanner Roark Did It — Can He Do It Again?

We’ve already spent some time with Tanner Roark’s breakout season and it’s mostly about that two-seamer and getting strike one if you ask him. Let’s focus on those things first.

The bad news first. First strike rate isn’t super sticky year-to-year. The correlation is .479 year-to-year, meaning that this year’s first strike rate describes 23% of the variance in next year’s first strike rate. That’s as weak as the year-to-year relationship of home runs per nine innings, or a little bit less than half as strongly correlated as strikeout rate.

Roark may have been above-average in that regard for two years, but that doesn’t mean he’s necessarily going to manage the feat again next year. If you throw 70% strikes on the first pitch, maybe batters start swinging more at the first pitch and then maybe you start throwing fewer first pitch strikes. However it works, this isn’t a skill we can bank on in a 200-inning sample.

The other part is a little more interesting maybe. Roark dropped his four-seamer almost entirely for the two-seamer and credits much of his success to that move. Look back at his ground-ball rate in his debut season, and everything looks great. But this past year, he had a blow-average ground-ball rate. Using a sinker as a fastball. What gives?

Looks like maybe the sinker’s not that great. Take a look at how it stacks up against the average two-seamer in certain important facets:

  Velocity PFx_x Pfx_z swSTR GB%
Tanner Roark 91.9 -7.3 8.1 5.3% 42%
League RHP 91.5 -4.9 6.2 5.6% 51%

At best, the pitch is average. With any degradation in velocity, though, it looks like it’ll be below-average.

Roark will still have some things going for him. His change (19% swSTR), slider (14% swSTR), and curve (15% swSTR) are all above-average by whiffs. That should be enough to keep his strikeout rate afloat, and it’s enough for us to try and find more Roarks in the future (as we have in the past).

Walk rate is decently sticky year-to-year, so he should still be above-average when it comes to command. But if the fastball is below-average, then you might have to believe the projections that give him a worse than league-average homer rate next year. That, along with all those balls in play with an iffy ground-ball rate, would actually probably produce a four-ish ERA.

Instead, you can probably split the difference. The secondary pitches seem legit, and the pitcher admitted he’s trying to improve them so that he can be less predictable (right now, he mostly uses the change against lefties and the breakers against righties). He has great command and pitches in the National League. He can probably still manage a mid-to-high threes ERA and a good WHIP just based on these facts alone. His team should give him some wins.

But if you have to pay for a sub-three ERA, you’ll be paying too much.

This is a pitcher that stands at the nexus of pitch-type peripheral analysis. How important is the fastball with respect to the rest of the pitches? How much should we weight movement and velocity over swinging strike and ground-ball outcomes? Those questions will take more time to figure out.

With a phone full of pictures of pitchers' fingers, strange beers, and his two toddler sons, Eno Sarris can be found at the ballpark or a brewery most days. Read him here, writing about the A's or Giants at The Athletic, or about beer at October. Follow him on Twitter @enosarris if you can handle the sandwiches and inanity.

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Heh-heh, blow-average.