Carlos Rodon didn’t have the time to make his initial pro-ball adjustments in the minor leagues. Less than a year after being drafted third overall by the Chicago White Sox in the 2014 amateur draft, he was summoned the majors. When Rodon got the call, he’d made all of eight minor-league starts and had thrown just 34.2 innings. So it’s not a surprise to see him find things along the way, like that moving toward the third-base side of the rubber halfway through his rookie year would help with his fleeting fastball command. That’s the sort of early-career adjustment that might typically happen out of the public eye, under the watch of a Double-A manager. Rodon’s not going to have the typical career. We’ll see nearly every adjustment he makes. We’re seeing one right now.

In the first major-league start of Rodon’s career, he threw 70 fastballs, 36 sliders, and two changeups. The fastball touches 97, and it’s not every day you see that from the left side by a starter. Of course he’d lean heavily on the fastball. The slider’s long drawn rave reviews. Baseball America called it “one of the best sliders college baseball has seen in years, a 70-grade pitch” in their 2015 preseason scouting report of Rodon. Of course he’d often go to the slider. But then there’s that “2” in the changeup column. BA said the changeup would flash plus, but lacked consistency. It’s what you hear so often from young pitchers as they look to differentiate themselves as a true starter among a pack of potential future relievers.

As expected from a pitcher with an inconsistent changeup, Rodon’s largely struggled against opposite-handed hitting. Oh, the fastball and slider have done a number on the same-handed bats. Rodon’s struck out more than a quarter of the lefties he’s faced with a league-average walk rate, allowing a .255 wOBA while running a 2.57 FIP. But the numbers against righties have evened things out — 4.44 FIP and .347 wOBA allowed — and Rodon’s faced more than three times as many righties.

But lately, there’s been a development. First being, Rodon’s been among baseball’s best pitchers in the month of August, running a 1.47 ERA and a 2.66 FIP over five starts. And while it’s easy to overlook a five-start stretch of dominance as being just five starts, it becomes harder to ignore those five starts when they coincide with this:

In this month, during which he’s dominated, Rodon’s thrown 91 changeups. In the four months prior, he threw a combined total of 115. The uptick began in Rodon’s first start following the All-Star break. Percentage rates are more telling.

Carlos Rodon changeup usage

Pre-ASB : 6.0%

: 6.0% Post-ASB: 17.3%

The changeup rate’s tripled. Righties have seen it a quarter of the time on the first pitch. He’s used it while behind, he’s used it while ahead, and he’s used it as a strikeout pitch. The usage figures alone indicate that Rodon’s developed a greater feel for the offering. His numbers during the usage spike support his decision. But we can dive deeper to figure out with what kind of a change Rodon’s working, and whether it might be here to stay.

When our own Jeff Sullivan wrote up Rodon’s slider back in February, he used the pitch’s velocity and movement readings to find an individual pitch comp, and found that, by the end of the year, the slider Rodon was throwing was almost identical in terms of velocity and movement to the slider thrown by Clayton Kershaw. Doing the same with the changeup, while folding in spin rate, we get Alex Wood, Gio Gonzalez and Matt Moore as our top three comps. Quality major leaguers with quality changeups. Only a little further down, we get Cole Hamels.

Rodon’s changeup gets 10 mph of separation from his fastball, an amount that typically makes for strong whiff rates. Rodon’s whiff rate on the change has been soundly above average. It’s shown both more horizontal and vertical movement than the average change, according to PITCHf/x. And when Rodon’s throwing it, he’s doing a better job of keeping it down in the zone, relative to the first half:

Let’s see it in action. It’s always instructive to see it in action. This comes against Miguel Sano, from Rodon’s first start following the All-Star break — the first start in which a greater emphasis on the changeup is noticeable. But before we see the changeup, let’s see a first-pitch fastball.

It’s a good fastball, a well located fastball, but it misses just inside for ball one. Now, behind in the count against a dangerous, opposite-handed hitter, Rodon needs a pitch he can trust to get back in the count while limiting damage. Sano wants the fastball. A slider breaking toward Sano’s barrel can be a frightening proposition. So Rodon goes to the pitch he didn’t have until recently:

It’s a pretty changeup, with noticeable late, arm-side fade away from Sano’s barrel. The rest of the at-bat goes: 1-1 changeup (swinging strike), 1-2 slider (foul), 1-2 changeup (ball), 2-2 fastball (foul), 2-2 changeup (swinging strike).

The last thing I wanted to do to measure the quality of the offering was to gain a sense of Rodon’s armspeed with the pitch. Any quality major-league changeup is thrown with the same armspeed as the fastball, so as to gain the full effect of the changeup looking like the fastball out of the hand, and to avoid the potential tipping of the pitch.

The armspeed?

If you can spot a noticeable difference, you’re seeing more than me.

What we have here appears to be a major-league pitch. We see good velocity separation with strong armspeed. We see plus tilt and fade. We find some encouraging comps. We notice an uptick in usage, indicating an improved feel, an assertion which the observed command of the pitch backs up. Command can come and go, and of course sustained command is the key, but he’s been demonstrating it lately (though it’s still certainly not as refined as it could be) and the quality of the pitch on its own appears promising, potentially leaving some room for error as far as the command is concerned. It’s the plus changeup Rodon flashed in the scouting reports, only the flashes are occurring more consistently. Carlos Rodon’s changeup is looking like a quality major-league pitch. And that sure goes a long way toward a quality major-league pitcher.