The Second Half’s Most Improved Changeup

As much as certain aspects of pitching remain a mystery when it comes to analytics, we’ve figured out a few things about the changeup. Like, movement is good! And like, a bigger velocity gap is good if you want whiffs! Those sorts of relationships can be identified pretty easily. And since movement and velocity become stable really quickly, you can cut this sort of thing into smaller samples and still get meaningful results.

You can ask things like: whose changeup improved the most in the second half, when it comes to things like velocity and movement differential off the fastball? And then you can get answers.

The answer to that particular question appears below in the form of a table. A detailed description of the data appears below the table, so you can click to see it. In short, I isolated changeup movement and velocity off of the fastball in both halves of the season and then compared second-half scores to first-half ones.

Here are the top-10 changeups in baseball by overall second-half improvement:

Second Half Changeup Improvers
Player Changeups 2nd Half CH Whiff% 2nd Half CH GB% 1st Half Z 2nd Half Z Diff Z
Dallas Keuchel 214 25% 75% 1.23 3.82 2.59
Lance Lynn 36 0% 44% -1.08 1.00 2.08
Robert Gsellman 114 13% 72% -1.30 0.64 1.95
Fernando Abad 76 9% 62% -1.83 0.04 1.87
T. Hildenberger 228 22% 85% 3.15 4.81 1.66
Mike Leake 178 6% 83% 0.29 1.92 1.62
Marco Gonzales 321 14% 65% -1.41 0.18 1.59
Jake Arrieta 100 17% 67% 0.65 2.20 1.55
Blake Treinen 53 25% 71% -0.24 1.29 1.53
Enny Romero 46 17% 67% -3.08 -1.58 1.49
Felix Pena 48 19% 100% -0.50 0.97 1.46
SOURCE: Pitch Info / Brooks Baseball
Full Data Description
In order to do this, I queried the Pitch Info / Brooks Baseball database to find all fastball and changeup movement and velocity numbers for the first and second halves. I defined changeup movement and velocity off of the fastball, using the four-seamer (unless a didn’t throw one) and keeping the definition fastball constant in both halves. I created z-scores for each quality of the pitch and then added them up for a changeup z-score in each half. Then I compared second-half combo z-scores to first-half ones.

Dallas Keuchel has always had a great change. The real development for him this past year was the four-seamer. It went from having four inches of fade to having none in the second half — almost like a cut fastball instead of a four-seamer — and that really fueled the difference in the changeup. The change itself didn’t see its movement altered much, though.

Trevor Hildenberger’s changeup got better in the second half, which probably helped him record one of the top-25 strikeout- and walk-rate differentials (K-BB%) over the latter half of the season. Mike Leake and Jake Arrieta saw their changeups improve from meh to better.

But maybe most impressive was the improvement in Lance Lynn’s changeup. It’s in a small sample, yes, but movement and velocity become meaningful very quickly. He’s been around for a while and has never had a good changeup. In the second half, though, he made incremental improvements on the pitch and it flashed potential.

Since the pitch itself changed — as opposed to the circumstances around it — and since Lynn is a free agent, this seems like a good time to take a deeper look. Let’s inspect how his movement and velo looked in both halves, set against the league average for right-handers in 2017.

Lance Lynn Changeup Improvement
Player Horizontal Move Vertical Move Velo Gap
Lynn First Half 1.9 3.4 7.7
MLB Average Righty 2.6 4.7 9.0
Lynn Second Half 3.0 4.1 8.2
SOURCE: Pitch Info / Brooks Baseball
Movement & velocity defined off four-seamer. A higher number is better.

As you can see, the changeup improved in all aspects. It was a gradual development, but the evidence is there.

Let’s look at pictures! Here’s a totally normal first-half changeup.

And now a second-half changeup that represents the new movement and velo well.

Obviously, this isn’t an ideally located pitch, but there’s more movement than the previous version of the change and it’s slower. Here’s the caveat, though: as is his wont, Lynn didn’t throw the changeup much (3% for the year), and threw it even less in the second half (2%). He didn’t get a whiff on the changeup in the second half, either. He loves to throw his fastballs. In the second half, he threw his cut, four-seam, and two-seam fastballs a whopping 93% of the time.

Lynn manipulates his fastball really well — Jeff Sullivan did a great deep dive on that ability — and the skill is part of why he’s been good despite lower strikeout rates. He’ll probably continue to vary his fastballs a lot with his new team — as Max Weinstein found in a deep dive on fastball mixers — but this changeup, and his cutter, offer a bit of upside beyond.

What if he mixed his fastballs for weak contact and called strikes, and also threw this better changeup and cutter more often for swinging strikes? As he continues to distance himself from a Tommy John procedure, his command should improve, as well, which could filter down into his non-fastballs as well.

The projections don’t paint a rosy picture for Lance Lynn’s 2018 season, so he might not cost much to his acquiring team. But not only is there an existing fastball-mixing skill that’s not currently captured by projections in his current arsenal, there’s potential for an emerging new pitch in there as well. Lynn’s an intriguing watch, and signing, for a guy who mostly throws fastballs.

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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I thought this was going to be about Robert Gsellman after first glancing at that table.