Michael Fulmer’s Trust Is Being Rewarded

Every spring, hopeful starters talk of new pitches with a gleam in their eyes. This changeup will change everything, they think. Then it comes to competitive games, and they don’t want to get beat on their fourth-best pitch, and everything goes back to where it was.

Detroit rookie Michael Fulmer had a similar story. He was flashing a plus changeup in bullpens, but not throwing it much in games. Then something changed, but he’s not sure what. From Anthony Fenech at the Detroit Free Press:

Michael Fulmer doesn’t know what happened.

He threw about 30 change-ups in one of his bullpen sessions before his start against the Rays on May 21 and something clicked.

Now, his catchers keep calling for that change-up.

“Sometimes, I’m shaking away from the change-up and they’re giving it to me again,” Fulmer said. “So, I’m like, ‘OK, I’ll throw it right here,’ and it usually works out, so by them calling it more, it’s giving me more options.”

I published a ranking last week at ESPN of the best pitches thrown by starters. Fulmer’s change doesn’t appear among the top ten. But it does appear 11th overall — and, for him, it’s impressive to see his third pitch turn up as one of the league’s best among starters (judged by z-scores for grounders and whiffs with a double weighting on whiffs).

What’s that thing Fulmer doesn’t understand, though? What changed about his changeup that made it better? Let’s look at some key stats over time.

It’s easy enough to see that his changeup usage took a big bump right when he said it did, and that it had more horizontal movement that day and going forward. Movement is huge for a changeup, especially since the velocity on the pitch has been a steady 85-86 mph all season.

But the source of that movement? Not a change in spin rates.

Michael Fulmer Changeup Spin Rate by Start
Date Spin Rate
7/6/16 1704
7/1/16 1815
6/22/16 1717
6/17/16 1847
6/12/16 1815
6/6/16 1743
6/1/16 1735
5/27/16 1716
5/21/16 1717
5/15/16 1734
5/10/16 1564
5/5/16 1846
SOURCE: Statcast
Trackman / observed spin rate.
Average for the season = 1733

For the changeup, you want a smaller spin rate for more drop, and so it’s not surprising that his steady spin rate has produced a steady level of drop. In any case, it’s not spin changes that have made Fulmer’s change better.

One thing that can change movement is arm slot. You get more horizontal movement if you drop down, and more ride if you move up. Arm slot doesn’t describe all of your movement, but enough that it could provide the inch or two of extra movement that Fulmer has found here. And would you look at that.

That May 21 date is highlighted, and that’s the day that Fulmer’s changeup release point — and, in fact, all of his release points — dropped down a bit.

According to the equation I found linking arm slot to movement, Fulmer’s change in arm slot would predict four inches of extra horizontal movement, and he’s gotten… four inches of extra horizontal movement since he changed his arm slot.

That might be enough to slam the ledger shut and light up a cigar, put the feet up and turn on the tube. But there’s a however. Because moving that arm slot changed the movement on all of his pitches. And indeed, you can see a lurch to left in all of Fulmer’s pitches if you check the chart near that Tampa start.

Mostly, pitches are defined in relationship to each other. Hitters set the fastball as the true center, and then everything diverts from that pitch. Is it possible that the true difference on his pitches didn’t change much, since all of his pitches changed? Let’s go back and look at his changeup movement, defined this time against his fastball movement.

Michael Fulmer Changeup Movement vs the Fastball by Start
Date True X Movement Change-4s Change-2s
7/6/16 -5.1 -4.4 0.2
7/1/16 -5.3 -6.3 -0.1
6/22/16 -7.5 -5.2 0
6/17/16 -7.4 -5 -0.8
6/12/16 -7.8 -5.6 -0.2
6/6/16 -5.7 -4.7 0.5
6/1/16 -7.1 -5.5 0.8
5/27/16 -6.1 -5.4 -0.1
5/21/16 -8.7 -6.9 -3.2
5/15/16 -7.6 -6.9 -0.9
5/10/16 -3 -2 4.3
5/5/16 -3.9 -3.8 2.7
4s = four-seam fastball, 2s = two-seam fastball.

This is murkier. Yes, his change gained movement against his four-seamer, but it’s now about equal to his two-seamer. And so we’ve come to the final bit of the adjustment. Since Fulmer’s slot changed, and his changeup movement became more similar to his two-seam movement, and departed from his four-seam movement, since May 21… Fulmer has decreased his two-seamer usage. Before that date, he used the two-seamer 30-40 times a game. In his last two starts, Fulmer has thrown 12 sinkers combined.

In the end, this story comes down to trust. Yes, Fulmer dropped his slot and gained an inch or two of movement on the changeup with respect to his four-seamer. But it was trust in that pitch that led him to start throwing the pitch more, realizing that it was better than his sinker, and moving to a pitch mix that made the most of his stuff. In a game of inches, trust means the most over 60 feet.

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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