Today on the front of the site, I wrote about Bronson Arroyo, and how he’s been better than his peripherals for five years now. The two-second version of the piece is that he’s played in front of a defense that was tops in the National League over that same time frame. The longer version led to a few more questions that I’d like to explore here.
One commenter brought up the fact that, yes Arroyo went to the sinker more, and yes the sinker traditionally has a worse BABIP than most pitches, but what if Arroyo’s sinker has a great BABIP. What if Arroyo’s sinker is a great pitch, not a league-average pitch? Fair point, despite pitch values making his ‘fastball’ a ‘fatball’ — the pitch is his lowest-rated, every year.
I pulled Arroyo’s results on his sinker for the last four years. And, lo and behold, his BABIP on the pitch is .274, not the .310 of a league-average sinker. But the team-based problem still exists. Is the pitch better than league average, or are the players behind him better at turning it into outs? We can see from pitch-type benchmarks and Arroyo’s results that the pitch is slightly better than average — he gets a 57% ground ball rate on it, average is 52%, but he also only gets ~4.5% whiffs on the pitch, and the benchmark is 5.1%. So, maybe the move to the sinker accounts for some part of Arroyo’s lower BABIP.
Another commenter brought up his different arm angles. Looks like he has two distinct arm angles for each pitch:
So let’s take a look at the difference in results on the sinker from the two angles. It’s slicing the data further, but it’s one pitch, and we might see why he does it. I separated the two clusters and dropped the pitches in the middle there so I could get the two extreme cases.
The first thing that jumps out from the numbers is that Arroyo drops to the low arm slot more for lefties. The ratio of righties to lefties at the high arm slot is .97, and from the low one it’s .51. There are more righties than lefties in general, but since he’s a righty, all the switch-hitters stand lefty against him. The swinging strike rate on those 225 pitches from the low arm slot to lefties goes up to 7.1%, so that’s nice. We risk slashing our sample too much if we look at the BABIP — only 56 balls in play from lefties off the low-arm slot sinker.
He’s never given up a home run off a lefty from that arm slot! That’s worth mentioning for a couple reasons. For one, lefties have taken him yard almost two times per nine innings over the past four years. Maybe he should drop down more often against lefties.
And for two, as one commenter pointed out, homers aren’t part of the BABIP equation. In fact, if you add them in to just the BABIP equation for his sinkers, his BABIP on that pitch would go from .274 to .308. Since Arroyo gives up so many home runs, and has played in front of a good defense, and switched to the sinker, perhaps we’ve explained most of his lower BABIP by now.
One last thing to look at is his control. It’s actually sort of amazing that he has had such good control. Even if you add his four-seamer to his sinker, he only throws a fastball 45% of the time. The fastball has the lowest ball rates. Check out the walk rates for starting pitchers that threw 46% or fewer fastballs last year:
Wow. What’s probably happening here is that if you don’t throw your fastball much, you better have great control of your secondary stuff or just great swing-and-miss stuff, or you’re in trouble. Like out of the league in trouble. So Arroyo has great control of secondary stuff, that puts him in good company. He throws the fastball really slow and not very often and doesn’t get many strikeouts, that puts him in bad company (see the comps on the front-page piece).
Is some of his control catcher-based? Ryan Hanigan is, by most accounts, a great framer. But this is yet another way back to team effects, seemingly. Unless… Harry Pavlidis is currently trying to figure out how much of framing is on the pitcher, and he’s found (in the early going) that Bronson is relatively easy to frame. So, maybe his soft stuff is easy to frame?
Unless Arroyo’s next catcher is at least a good framer, and his next defense is a great defense, and his next park is friendler to pitchers — after all, he’s only getting older, and worse — then there’s a lot of reasons to be nervous about his production going forward. Even if he’ll still be throwing that sinker out of two arm slots.
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