Tarik Skubal's ascendance to an MLB ace began on April 30, 2021. That day was the genesis of what's become one of baseball's most unhittable pitches: Skubal's changeup.

Skubal enters Wednesday's start against the World Series champion Rangers as the most valuable pitcher in the Majors over the last 10 months. The 27-year-old southpaw has a 2.67 ERA and 122 strikeouts in the 18 starts since he returned to the Tigers rotation last July. And the changeup is the pitch that truly transformed Skubal into a 2024 Cy Young contender.

• See where Skubal lands on latest Cy Young poll

Skubal's changeup is a unique weapon. It is a seam-shifted wake changeup -- the way he throws it, the seams of the baseball catch the air in just the right way and make his changeup move much more, and much more unpredictably, than it would otherwise.

It drops. It fades. It dances through the air. And hitters swing and miss, more often than they do against any other starter's changeup. All because of the way Skubal orients the seams of the baseball when he releases the pitch.

"Hitters have a harder time picking it up," Skubal told MLB.com. "Because it's supposed to be doing one thing, and it does something else. There's physics that go into it: The friction of the ball, how the seams catch, how the smooth air can push it."

SP with highest whiff rate on an offspeed pitch, since July 2023

1. Kodai Senga -- forkball: 60.1%
2. Tarik Skubal -- changeup: 50.0%
3. Patrick Sandoval -- changeup: 47.5%
4. Blake Snell -- changeup: 44.4%
5. Tyler Anderson -- changeup: 43.1%

Skubal didn't just find that magical changeup overnight. Its development has been a three-year-long process.

Here's how Skubal's changeup became what it is today -- a Cy Young-caliber pitch.

Between 2020 and 2021, following his rookie season in Detroit, Skubal went to Driveline Baseball -- "to find a changeup." He ended up with a splitter. The data supported the idea that it would fit well with his arsenal.

But as his sophomore season began, Skubal found he couldn't command that splitter.

"It was a waste pitch," Skubal said. "Every time they called it, it was just, 'Ball.' Guys just stopped swinging at it. Because why would you swing at something that's never in the strike zone?"

His April 30, 2021, start against the Yankees in New York was the turning point. After that outing, Skubal sat down with manager A.J. Hinch and pitching coach Chris Fetter.

Their message to Skubal: "Hey, you need to throw your changeup again. The splitter is not good."

So Skubal scrapped the splitter, a month after he'd introduced it. He went back to the changeup he'd thrown as a rookie -- which wasn't as nasty from a pure "stuff" perspective, but had gotten better results -- and strung together a reasonably productive rest of the season.

But he wasn't satisfied. Skubal's old changeup wasn't dropping enough; he wanted to improve the movement. So heading into 2022, he changed his grip, from a traditional, four-seam changeup grip to a two-seam grip. That helped, but he wanted more.

"I still didn't love it. I wasn't in love with it," Skubal said.

The 2022 version of Skubal's changeup required him to pronate during his delivery -- turn his wrist over to create the movement of the pitch -- and Skubal, by his own admission, is not good at pronating. So he wound up turning to his slider as his main offspeed offering.

"I threw a ton of sliders in '22," Skubal said. "That was my change-of-pace pitch. I basically used it as a changeup."

To some extent, that worked. Skubal was having a breakout season. Then he got hurt. In August 2022, Skubal underwent elbow surgery to repair his left flexor tendon. He had to rehab for nearly a full year.

But that was also when the big change finally happened that unlocked Skubal's changeup -- and unlocked ace-level Skubal. He discovered seam-shifted wake.

Seam-shifted wake -- the way the orientation of the baseball's seams affects how it moves through the air -- is a fairly new phenomenon in baseball. The Tigers' pitching lab, on the cutting edge of pitch design, saw Skubal as a prime candidate to take advantage of it, specifically by throwing a seam-shifted wake changeup.

Tigers president of baseball operations Scott Harris thought Skubal could be a poster child for seam-shifted wake. He told the southpaw that the way his body moved, the pitch should come out of his hand in the ideal way.

To teach Skubal his new changeup, the Tigers gave him a baseball with a black dot painted on it inside the seam's horseshoe. They told him to throw his changeup while trying to keep the dot at the top of the ball -- that would mean the baseball was spinning in the perfect direction for the air to catch the seams and propel it down and to the arm side. It would create the movement Skubal's changeup had always lacked.

Skubal learned how to execute that changeup successfully, with the help of a mental cue Detroit gave him: Try to swipe across the face of the baseball and cut it. The changeup wouldn't actually cut -- it would actually drop and fade, much more than usual -- but Skubal thinking about cutting it would get the seams into the right position.

"That's how seam shift and seam effects come into play," Skubal said, "and push the ball down and make it run that way."

Skubal was a natural. The Tigers' pitching gurus, Fetter and assistant pitching coach Robin Lund, told him: "This is you. This is what we think can be really good for you."

"Right when I started throwing it, the feedback of that little dot was huge," Skubal said. "I just started chasing that, and then it came pretty naturally. So exactly how they thought it would go … it went that way. It was a pretty easy transition."

Skubal harnessed seam-shifted wake, and his changeup blossomed into a wipeout pitch. He recorded 35 strikeouts on changeups when he returned in 2023, and has recorded eight so far in 2024. Opposing hitters have struck out in 43% of the plate appearances decided by Skubal's seam-shifted wake changeup over that span.

And it's no wonder, because Skubal's changeup is moving in a way it never had before.

The evolution of Skubal's offspeed pitch movement

• 2020, original changeup: 83.2 mph / 24.9" of drop / 9.4" of run
• 2021, splitter: 85.1 mph / 28.2" of drop / 9.9" of run
• 2021, back to changeup: 82.1 mph / 28.5" of drop / 8.7" of run
• 2022, new grip: 83.6 mph / 32.5" of drop / 13.4" of run
• 2023-24, SSW changeup: 84.3 mph / 33.4" of drop / 13.5" of run

It is moving more in total, and moving more deceptively, all at a higher velocity than it used to be and with an 11-12 mph differential from his fastball, which sits right around 96 mph. And Skubal's new changeup isn't some mysterious pitch sorcery. We actually know the difference is coming from the seams.

Statcast tracks the spin axis of every changeup Skubal throws, revealing how the pitch behaves on its trajectory to the batter and measuring how much of the pitch movement is due to seam-shifted wake.

When Skubal was throwing his original changeup as a rookie, barely any of his changeups had seam-shifted wake movement. Now, nearly all of his changeups do. His switch to a two-seam grip in 2022 got the process started, and chasing seam-induced movement over the last two seasons has taken Skubal to an even higher level.

% of Skubal's changeups with SSW movement by season

• 2020: 17%
• 2021: 35%
• 2022: 76%
• 2023: 83%
• 2024: 86%

This is important because of the hitter's perception: Batters think Skubal's changeup is going to move a certain way, and it ends up moving much differently.

Statcast's spin axis data shows us that Skubal's changeup is moving one way out of his hand, but by the time it gets to the plate, the path of the pitch has deviated significantly from that initial movement -- as if Skubal had spun the ball a completely different way.

The reason for the change in direction is that the air has caught the baseball's seams along the way and given it a new kind of movement. That is seam-shifted wake in a nutshell. That is what the Tigers taught Skubal.

"What they're saying, they're telling me with confidence," Skubal said with a laugh. "So I buy into it. They've always guided me in the right direction."

And he understands the fundamentals of what his changeup is doing, even if seam effects can be tricky to explain.

"I'm gonna butcher this -- but they basically explained to me the tilt of the ball, vs. the measured [movement]," Skubal said. "Say I release it on one axis -- the seam effects actually make it behave like it's on a different axis."

Skubal held up an imaginary baseball in his left hand to illustrate.

"So you're getting the shape of a pitch that you'd be throwing by releasing it here" -- he demonstrated a changeup grip rotated sideways from the one he throws. Then he turned his hand back to his actual grip -- "but you're actually releasing it here."

For Skubal, that never used to be the case. When he first got to the big leagues, his changeup movement was exactly the same when it left his hand as when it got to the batter. Only now does he have the extra layer of deception.

Skubal's new changeup movement did necessitate one key adjustment: He had to shift his target so the pitch would finish in the spot he wanted.

"I don't know if all pitchers feel this way, but it's really hard to buy into throwing a pitch to a spot that you're not comfortable with, and just trusting that the ball will go that way," Skubal said. "Because you've done it so many times … right there, right there, right there … and now I need to be comfortable moving to a new target to get there. That was probably the toughest task, just getting it over the strike zone to get guys to swing at it."

Skubal had to force himself to trust himself: "That I can throw it this way, and it's not gonna cut, it's actually gonna come back."

"That's something that I hadn't done before," he said. And it took some time.

But by now, Skubal has mastered his changeup. Now he has one mantra: Over the plate and in the air. He lets the changeup's natural movement take it from there.

"You know, the plate's this wide," Skubal said. "And if now I can throw changeups that start here and end there? It's opened up a ton for me."