A Fascinating In-Game Pitching Adjustment

Anthony DeSclafani put up a clunker last Monday. He gave up five runs and 10 hits over seven innings — to the Nationals of all teams — and the Giants lost 5-1. That’s nothing out of the ordinary; good pitchers have bad outings all the time. DeSclafani has been solid in San Francisco, but he’s more above average than elite. Giving up five runs is hardly an earth-shattering outcome.

Would you find that start more interesting if I told you that all five runs came in the first inning? Probably – that’s a lot of runs to give up in one inning followed by six clean sheets. On the other hand, that’s baseball: sometimes you’re the steamroller, and sometimes the other team has your number for 15 minutes.

Afterwards, though, Maria Guardado’s game story had an interesting detail:

“After the rough start, DeSclafani convened with pitching coach Andrew Bailey in the dugout and learned that he wasn’t getting his optimal shapes on his slider and his two-seamer. He made a mechanical adjustment between innings, tweaking the way he took the ball out of his glove…”

For 100 years, that wouldn’t have been a particularly interesting quote. That’s just the kind of thing that pitchers and pitching coaches say after bad outings. “Oh, I/he was doing this thing wrong, as you can see from the runs. But then we changed that thing, as you can see from the lack of runs afterwards.” But these days, we can go to the tape.

Did Bailey see something? Let’s reconstruct the data that he was getting. Here are velocity, release point, and movement data for DeSclafani’s first seven first innings. First, the sinker:

Boy, that’s a lot of numbers! One thing stands out, though: his sinker wasn’t sinking. The key column, in my eyes, is vertical movement with gravity included. In the first inning of the game on May 8, his sinker was falling roughly two inches less on its path from hand to home than it had earlier in the year. That’s because he was imparting two extra inches of ride on it, as you can see from vertical movement without gravity included. This wasn’t some case of first-inning energy making him throw differently, either: we’re comparing only to previous first innings. Sinkers should sink; this seems bad.

What about his slider? Here’s the same table:

Similarly, his slider had a shape issue. It got three inches less horizontal movement than average in that fateful first inning, and nearly an extra inch of vertical ride, so it fell less and also broke less on its flight home. Both pitches, in other words, were straighter than expected. That’s not a good way to get by in baseball these days. Hitters are just too good.

In that inning, the hitters were indeed too good for DeSclafani. They swung at six sliders and only missed one. They swung at six sinkers and made contact with every single one. The results? Two foul balls, three hard-hit balls that all went for hits, and a soft line drive single. He wasn’t fooling anyone, in other words.

Is that what Bailey was looking at, and what he and DeSclafani discussed after the first? I don’t know, but it sure seems that way. He certainly wasn’t getting the optimal shape on either of his pitches, despite velocity that was quite close to average.

What happened after the first inning? Like the article said, DeSclafani made a mechanical adjustment. Let’s look at the numbers. First, the sinker:

Then, the slider:

One quick nit-picky note: those yearly averages are for innings beyond the first, just to compare apples to apples.

Just like that, he was fixed! His sinker started to sink again. His slider slid and dipped more. Sure, he didn’t hit his yearly averages on the nose, but I’m more interested in the direction of change. You can see the intent in both pitches, and it logically follows that both come from the same mechanical change: both pitches started to have more horizontal break and less vertical, which makes sense to me.

Now, DeSclafani’s pitches didn’t improve as much as his six scoreless innings might suggest. He didn’t suddenly turn into peak Jacob deGrom; his sinker induced exactly zero whiffs the rest of the outing, and his slider only got two. Those six innings of work, in fact, only produced two strikeouts, and they came with a walk and a hit by pitch. Bailey and DeSclafani didn’t spin straw into gold; they just moved him from overmatched to competitive.

But that’s who DeSclafani is, even when he’s at his best; a competitive pitcher who isn’t easy to square up and who doesn’t give out free passes. The Nats have the lowest strikeout rate in baseball, for all the good that’s done them. It’s clear to me that what looked like a throwaway quote – “Oh, I gave up some runs, so the pitching coach suggested I change things.” – hinted at how the Giants monitor their pitchers.

One quick note before we move on: I watched a lot of footage from this game trying to isolate any mechanical changes, and I couldn’t do it. I’m not particularly surprised by that. As DeSclafani noted, the change was tiny: he altered how he was taking the ball out of his glove. That implies to me that his grip was slightly different, but as far as I could tell, he didn’t change anything else about his delivery.

Luckily, DeSclafani has pitched again since this game, so we can see whether the fixes took. Maddeningly, the answer is unclear. His sinker had more vertical ride than ever, so much so that he basically scrapped it until he could fix the shape. His slider, on the other hand, was back better than ever, with plenty of horizontal bite. He didn’t allow a run in a perfect first inning. Hey, they did it!

Except they didn’t do it. Baseball is hard. The first three Diamondbacks he faced in the sixth inning of that game all reached, and then DeSclafani left the game thanks to an injury. What injury, you might ask? Oh, dropping a piano bench on his toe a few weeks ago, naturally. You can use all the fancy pitch dashboards you want. Baseball defies easy analysis.

Jeff Zimmerman clued me in to the quote that led to this article. Thanks, Jeff!