A tough thing about analyzing pitching is that it’s a moving target. You can get a decent sense of what a pitcher is like right now, and then he can completely change his approach over the next month and become a different pitcher. There’s evidence of this in the data: a pitcher’s exit velocity becomes stable relatively quickly, but then that stat’s predictability doesn’t actually improve as the sample increases. In other words, you can see what the pitcher’s got now, but what about tomorrow? Ask us then.

This is all relevant to Tyler Chatwood. You might have thought you had an idea of who he was as a pitcher — great sinker, uses his four-seamer for whiffs, and doesn’t have great secondary stuff, so it’s all about the ground balls. That’s who he was! It isn’t who he is right now, though. I had to ask him about who he is right now when I had the chance.

Let’s first use the numbers to describe the difference. You’ll see big differences pop out, but it helps to highlight.

Tyler Chatwoods in Two Aprils April 2016 % Used Velocity H-Mov Y-Mov Sinker 40% 92.7 -6.1 7.5 Fourseam 34% 92.9 -0.5 8.4 Slider 16% 87.3 2.0 2.3 Curve 5% 77.3 4.6 -7.3 Change 5% 84.5 -4.5 7.0 April 2017 % Used Velocity H-Mov Y-Mov Sinker 27% 94.3 -6.1 9.1 Fourseam 37% 94.8 -0.6 10.8 Slider 19% 89.4 2.3 3.3 Curve 7% 77.9 3.4 -8.3 Change 10% 87.9 -3.9 5.9 SOURCE: Brooks Baseball

Yeah, so, Chatwood, what’s up with that changeup? “It’s good right now, I’m getting a lot of swings and misses,” he said with a smile before a game with the Giants this month. It’s better because of a combination of mechanics and attitude on the pitch.

The pitcher did adjust how he throws the change. It’s the same grip, but thrown differently. “Just switched the way I throw it in my hand,” Chatwood said. “Grip it like my sinker and throw it off the fingers.” He switched the seams slightly, from a four-seam-type changeup grip to a two-seam one, and that may be why it’s getting more sink right now. Relative to his four-seam fastball, it’s dropping five inches now, and it used to drop an inch and a half.

It does look like all of Chatwood’s pitches have more “ride,” so some of this could be due to calibration issues in the pitch-tracking data, so it’s good to know that some of the added confidence in the changeup has come from a mental change as well. “I always used to try to make it move rather than just throw it,” he admitted. “Mine’s hard right now, but I’m getting swings and misses, because the arm speed is a big deal.” Relevant: the swing rate on the change is up to 60% from 40% last year.

The Rockies’ righty has doubled his usage of the pitch, and though the velocity gap is smaller (6.9 mph now, down from 8.4), the movement looks like it’s improved. Confidence in the pitch has rewarded him with whiffs on nearly a quarter of the changeups he’s thrown, which has contributed to the best swinging-strike rate he’s shown since A-ball with the Angels (minimum 20 innings thrown).

The changeup used to look like this:

Now it looks like this:

But if you scan back up to that first chart, you’ll notice other differences. His velocity is up, and this is comparing like to like, so it’s real. “At the end of the year last year I was throwing around this hard,” Chatwood pointed out. “I just kinda got stronger coming off surgery and gained confidence in how I feel. This year, right out of spring training, I felt good.”

If you ever feel like a nerd looking up this sort of stuff, stroking your chin, and saying, “Ah, yes, it does look like he’s been ramping up the velo,’ know that the players are doing the same thing these days. “I look at those spin rates, and I saw my curve is around 3000, so I started throwing it some more,” said Chatwood with a smile. And look at that: Chatwood has a top-10 spin rate on his curveball.

That high-spin curve is pairing well with his high-spin four-seamer, especially at the new velocity. He’s thrown 38 this year, and every single swing on the pitch has produced either a strike (via foul or whiff) or a ground ball. Not bad for a pitch. Even though his results on the pitch have been average so far in his career, this chart from my colleague Jeff Zimmerman relating velocity and spin rate to swinging-strike rates for curves does suggest that spin is useful for the pitch. The righty’s decision to throw it more often seems like a good one.

There’s a real opportunity for Chatwood to be the best version of himself here. If he pairs that plus ground-ball rate (58% since the beginning of last year) with the new whiff rate (9.7% currently), he’d be in rare territory. Only three starting pitchers last year had a ground ball-rate over 50% and a better swinging-strike rate: Jake Arrieta, Francisco Liriano, and Noah Syndergaard. Dallas Keuchel (9.6%) was right there, too, and provides some insight into where Chatwood may be going with these latest tweaks to his arsenal.

Of course, that was 2016 Dallas Keuchel. We’d have to dive back in to figure out who Dallas Keuchel is right now.