How the Pirates’ Mitch Keller transformed himself from one of MLB’s worst pitchers

On April 5 at Fenway Park, Mitch Keller had just begun his third tour through the Red Sox order by walking the leadoff man to bring up Rafael Devers, who according to the scoreboard was batting .308 with a .833 OPS. Those small-sample stats only carried significance because at that moment they almost exactly mirrored Keller’s career numbers against left-handed hitters — .308 batting average, .837 OPS — and because a scoreless gem hung in the balance.

Devers saw the kitchen sink. A changeup for a called strike. A well-placed sinker fouled away. A curveball Devers didn’t chase. A foul ball on an elevated fastball. Another foul on an inside cutter. Then back to the four-seamer, in on the hands, for a jam shot to second base that turned into an inning-ending double play. Threat neutralized. Six pitches. Five pitch types. No cookies.

This is not the old Mitch Keller.

At 27, Keller is the pitcher experts projected him to be when he was ascending prospect rankings years ago: atop the Pirates rotation, taking the baseball every fifth day and dealing. It just took five years to get there.

“He’s our big dog,” catcher Austin Hedges said after Keller tossed his first complete game and shutout Monday against Colorado, dropping his ERA to 2.72. “I don’t care who we’re facing, I’ll take Mitch Keller versus anybody in the league right now.”

If you’re a fan of finding sentences that have never been uttered before, there’s one. This version of Keller hasn’t existed long. His next start Sunday falls exactly a year from the date the Pirates bumped him to the bullpen following back-to-back bad starts against the Reds. That demotion was an inflection point.

There’s the Keller before: 203 innings, 6.12 ERA

And the Keller since: 176 innings, 3.07 ERA

“It’s fun to watch, man,” says Andrew McCutchen, who was the reigning NL MVP when the Pirates drafted Keller in the second round in 2014. “He’s your No. 1. He’s going to be a No. 1 for a long time.”

Keller, on track to hit free agency after the 2025 season, revealed in a radio interview this week that he and the Pirates have had preliminary conversations on a contract extension. GM Ben Cherington told The Athletic the Pirates would like to keep Keller long-term, and they’re not opposed to in-season negotiations (as evidenced by the Bryan Reynolds extension), but as of now there’s no news.

“There’s a category of players that check off boxes that would make us want the door to be open to that type of thing,” Cherington said Wednesday. “Mitch checks those boxes. That’s as much as there is to share.”

The Athletic’s Tim Britton recently drew up a hypothetical extension for Keller of five years and $45 million, with a club option taking it to six years and $57 million. Every extension is a risk/reward proposition for both sides. Keller’s feels more extreme than most. Keeping Keller through his prime at an average annual value around $9 million or $10 million could be a big bargain for the Pirates, who haven’t signed a starter to an extension since Charlie Morton in 2013. But it also would be a significant bet on this version of Keller being here to stay.

The fact they’re having those conversations at all is a sign of how far Keller has come. His growth and evolution are, in part, a testament to this era of pitching development. His reemergence relied on rewiring his mechanics, expanding his repertoire and recapturing lost velocity. That did not occur overnight. But after so many times thinking he’d reached rock bottom in his baseball career, only to hit a new low afterward, Keller was ready for a full-scale overhaul. He had accepted what big-league hitters and their bats had made clear to him, loudly and repeatedly: What had gotten him to the majors wouldn’t work there.

When Devin Hayes, a performance coordinator at Tread Athletics, had his first video call with Keller shortly after the 2021 season, Keller was not particularly enjoying the game of baseball. He was back home in Cedar Rapids, Iowa, after turning in a 6.17 ERA in his third MLB season, completing six innings only once and spending two summer months at Triple A. Hayes showed Keller two clips. The first was a four-seamer from Keller’s last start of the season, in which his fastball averaged 92.3 mph. The second was a clip of the fastest pitch Hayes could find of Keller throwing: a 99 mph heater years earlier in the minors.

“This is probably one of the best days of you throwing a baseball in your life,” Hayes said. “Your body is capable of that. What were you doing on that day?”

This was the first step of Keller’s reinvention: bringing his fastball back to life.

But a lot had happened since 99 mph in the minors. A series of unfortunate events and crooked numbers. There was the best day of his baseball life going off the rails; his first inning in the majors went walk, single, walk, strikeout, single, grand slam, fly out, double, single, single, strikeout. There were three other starts in his rookie season even worse than that one. There was the 2020 season when he missed bats and also the strike zone, with twice as many walks as hits allowed. Then, in 2021, he started to truly look lost on the mound. He was weaponless and at the mercy of the hitters he was unable to put away. In his June 10, 2021, home start against the Dodgers, he was yanked in the third inning — he hadn’t made it through four innings in half of his 12 starts — as his ERA soared above 7. Keller rarely showed it outwardly, but it all was eating at him. “I’m probably the most pissed-off guy in this locker room,” he said after that start. His mechanics were messy, his execution missing, his confidence blown. He was fully out of sync, not a tweak or two from things clicking.

“When (the mechanics and tempo) all feel good, then the other stuff you can take care of with tinkering,” Keller says now, looking back at the start that precipitated his trip to Triple A. “But when everything feels off, you can’t even tinker. Nothing is consistent. That’s where that frustration was coming from.”

At the end of the 2021 season, as executives and coaches mapped out offseason plans for players, there came a comment from the Pirates performance staff that caught Cherington’s attention: His body is really strong. It struck Cherington that it wasn’t input he typically got about a struggling player. “I remember hearing that and a bulb going off,” Cherington says. “OK, well then that’s something to build off of.” Keller was strong. He just needed to move more efficiently.

That’s how he’d get back to 99 mph.

Keller came to Tread on the recommendation of a former teammate, Clay Holmes, a failed-starter-turned-reliever who had honed his devastating sinker at Tread, been traded to the Yankees and worked his way toward the back end of their bullpen. Pirates pitching coach Oscar Marin had previously collaborated with Tread co-founder Ben Brewster on training programs for Holmes and a few others, so when Keller joined Tread the Pirates knew he was in good hands even if — as they expected might happen — a lockout cut off the club’s communication with players that offseason.

Keller set to work with Hayes to recreate the mechanics that had gotten him to the majors. They used plyo balls and an alliterative mantra — timing, tempo, tilt — to lengthen his arm action. They focused on drift (a pitcher moving his center of mass forward during the leg lift before driving off the back leg) to build momentum down the mound. They deployed the “Kikuchi Drill,” named after Blue Jays starter Yusei Kikuchi, to address drift and train the body to stay as tall as possible for as long as possible during the delivery.

As Keller ramped up in his offseason progression, inching back into the range of 90 mph in flat-ground throwing, Hayes figured a little competition might light a fire under Keller. Hayes, a former Division III pitcher, was throwing bullpen sessions at the time. He started sending Keller a video of his fastest pitch from each week. One week, his radar gun flashed 90.8 mph.

“I’m going to throw harder than you,” Hayes texted. “You can’t let that happen.”

The next week, Keller hit 94 mph. He shot a text back.

“You’re never going to throw harder than me again.”

In late January 2022, amid the MLB lockout, Keller made a trip to Tread’s facility in Hickory, N.C., and video of his bullpen session went viral. Keller stepped on the mound and started firing. He hit 99.5 mph. Then, as the session wrapped up, Keller turned to Hayes and said, “I think I can let two eat here.” The next pitch was 100.4 mph. The last one was 100.9 mph.

“I sacrificed my shoulder for Mitch last year just from throwing against him every week,” Hayes says with a laugh. “It has not been the same since then.”

Less than four months later, on May 18, 2022, the bullpen door at Wrigley Field swung open in the third inning and Keller emerged for his first appearance out of the Pirates ’pen. His velocity was up two ticks year over year, now sitting 95 mph and topping out at 98 mph, but the results remained miserable. Nothing made that more clear than the graphic the YouTube broadcast aired that day.

“Worst, worst, worst, worst, worst,” Keller’s dad, Al, says almost a year later. “Oh yeah, I’ve seen it. You’re like, oh my God, really? I guess someone has to be there. But it sucks when it’s your kid.”

That screenshot tends to resurface and be shared on social media now whenever Keller delivers a strong start. But there was another clip from that game that actually signaled Keller’s new direction. It happened after he struck out the first two Cubs in the third inning. Willson Contreras stepped to the plate, and Keller whistled a first pitch that ran inside and hit Contreras.

“I was like, that’s the sinker!” Hayes says. “That’s sick. I don’t care that you hit him. We can use that.”

See, as opposed to a year earlier, when Keller was out of sync and sent to the minors, he actually felt this time that he was close to breaking through. Cherington says the Pirates also felt he was in a much better spot, despite the surface results. His mechanics were clean, his execution improving, his confidence bouncing back. “I felt good but wasn’t getting results, so something had to change,” Keller recalls. That left one obvious area to address: his arsenal.

The day Keller was demoted to the bullpen, Hayes scoured Edgertronic video from recent bullpen sessions and noticed Keller was cutting his four-seamer. Instead of the ball coming out of his hand with true backspin, it was cutting considerably, leading to a fastball with inefficient spin. One solution would be to work to fix the four-seamer and increase its carry. Another would be to lean into the natural movement, shift the grip and turn it into a two-seamer.

Hayes created a three-minute video of Keller’s four-seamers to show other Tread instructors. They saw what he saw. Their internal numbers said Keller had similar spin efficiency, axis and tilt to Holmes. He could be a natural with a sinker. Hayes sent Keller the video, explained what he saw and suggested he’d be a good candidate for a seam-shift sinker. The Pirates, it turned out, were on a similar page. Marin watched Keller test out the sinker while playing catch, then take it to the bullpen. They all liked how it looked. “It was kind of gross,” Keller says.

Keller hadn’t thrown a sinker since he was 10, and even that was only because of a “stupid superstition,” he says. He had it in his head back then that the way to throw strikes was to alternate each pitch between the four-seamer and the two-seamer grips. So he’d let a four-seamer fly past flailing 10-year-olds, then switch to a sinker that didn’t sink and keep pouring in strikes. “I don’t know why I remember that,” Keller says, laughing. “I thought that was why I threw strikes. But I guess it was just because I was a good pitcher.”

The next sinker Keller threw in a game was the one Contreras wore.

Undeterred, Keller returned to the rotation in late May 2022 and unleashed 34 sinkers while tossing five innings of two-run baseball against the Dodgers. Then he held the Tigers to one earned run, the Cardinals to two and the Giants to one. “It was like, holy s—, this is electric,” Hayes said. Because the sinker added east-west action to a pitch mix that had previously run mostly north-south (four-seamer, curveball, changeup), Keller also added a sweeper he had toyed with during the offseason.

Over the remainder of the season, Keller’s ERA fell into the 5s, then the 4s, then the 3s. The other shoe never dropped. Bad starts didn’t snowball. Good ones no longer felt fluky. Broadcast graphics started to show something other than worst, worst, worst, worst, worst. “It was like, OK, this is kind of real now,” his dad says.

Back in Boston this April, Hayes sat in the stands on the third-base side with a few college buddies trying to get side-view video of Keller dicing up the Red Sox. It was his first time seeing Keller start in person. After the Devers double play, Keller surrendered a run on a seventh-inning infield single and avoided a three-run homer when replay concluded Reese McGuire’s fly ball had curled just to the right of Pesky’s Pole. Keller punched out McGuire, took home the win and invited Hayes and his friends onto the field afterward.

“It was probably one of the better days of my life, for all of it to come together,” Hayes said.

Keller’s evolution continued this past offseason, building off the skill and mechanics improvements he’s made over the past 18 months. Even with the better results in the back half of last season, Keller still was handcuffed to some degree. Left-handed hitters saw mostly four-seamers, sinkers and curveballs and continued to punish his inability to put them away. So Keller spent the winter months developing a cutter — a variation of the gyro slider he threw in 2019 — that fits somewhere between his horizontal (sinker, sweeper) and vertical offerings (four-seamer, curveball, changeup). The cutter has effectively replaced the sinker against lefties, and using it to get in on the hands has helped the four-seamer play up. So far this season, Keller has attacked lefties with 35.4 percent four-seamers, 27.5 cutters and 20 percent curves.

Mitch Keller vs. LHH

YEARAVGOBPSLGK%BB%

2021

.345

.419

.477

14.3

11.7

2022

.276

.359

.390

16.7

10.3

2023

.202

.265

.340

29.4

7.8

When he was a prospect, Keller’s favorite pitch to throw was his fastball. Last year, it was the sinker. Now it’s the sweeper. “When it’s on, it’s a fun pitch to throw,” he says. Devers didn’t even see that pitch. The sweeper grades as Keller’s best pitch by Tread’s internal metrics — which suggest he has four plus major-league pitches — but he’s only throwing it 12.7 percent of the time because he’s been able to get ahead in counts and finish hitters off with other pitches. By Stuff+, Keller’s sweeper is the second-best slider among qualified starters, behind Graham Ashcraft and just ahead of Gerrit Cole and Shohei Ohtani.

Hayes says Keller has the potential and pitch mix to be like 2022 Joe Musgrove, to have six pitches and the confidence to throw them in any count. Keller used to love his four-seamer. He threw it 55 to 60 percent of the time before last season. He even favored it when ahead in counts and in need of a whiff. Now Keller throws it a quarter of the time. Recently, Hayes joked to Keller, “Honestly, don’t throw the four-seam unless you’re going to throw it 100.” The velocity is still there when he needs it, like when he touched 97 mph in the ninth inning Monday. But there’s a lot else in the tank, too. “You’re pitching now,” Hayes says. “You have other things you can throw in any count that just make you a nightmare for hitters.”

Statcast: Keller’s pitch mix

pitch

percent

mph

avg

slg

whiff%

4-Seam Fastball

25.9

95.5

.185

.296

30

Cutter

24.3

90.7

.182

.364

24.2

Sinker

19.8

94.1

.238

.333

8.8

Curveball

12.8

78.1

.188

.250

16.3

Sweeper

12.7

83.1

.182

.273

26.8

Changeup

4.5

91

.556

.667

17.6

Cherington says credit for the transformation belongs first and foremost with Keller, but it also is an important sign and step forward for the staff in Pittsburgh — an organization that cleaned house before Cherington’s arrival in large part because of its failure to help pitchers reach their full potential.

“We know we need to be good at pitching development over time,” Cherington said. “Obviously, that’s something that’s important to us. We believe we’re making progress. It does help to have models of what that can look like — mostly because I think it helps our confidence in applying some of what we’ve learned through the experience with Mitch to other guys. It’s not always going to take the same path. Everyone is different. But these things are important to the momentum of the broader pitching effort, too.”

At his parents’ home in Cedar Rapids on Monday, Keller’s mom, Joni, started pacing as Keller headed back out for the ninth inning.

“I’m nervous,” she said.

“Why?” her husband asked. “Didn’t you watch the first eight innings?”

Baseball has become fun again for Keller, and for his family. There’s no telling where this season will wind up for the first-place Pirates and their No. 1 starter, but he has learned through the highs and the lows (and the very lows) to appreciate the moment. After all, he says, these days are a lot better than the ones when he had no answers, when he was beat up by the big leagues, when he found himself contemplating his next career after baseball.

“You get to those points, and it sucks,” Keller says, leaning against the railing of the visiting dugout at Fenway Park. “I was looking at things I liked to do and seeing what jobs were out there. That might be taking it to an extreme, but in those dark times, yeah, I feel like there’s nothing else to do.” He shakes his head, then smiles. “I’m glad I’m not in that headspace anymore.”

(Top photo: Gene J. Puskar / Associated Press)