It's all coming together for Detroit Tigers' Jack Flaherty thanks to unlocked slider

KANSAS CITY, Mo. — It's all coming together for Jack Flaherty.

The 28-year-old signed a one-year, $14 million contract with the Detroit Tigers in free agency, betting on himself to bounce back and trusting new pitching coaches to help him find a fix. The deal came together in mid-December, then he ramped up his offseason work with pitching coach Chris Fetter and assistant pitching coach Robin Lund analyzing his bullpen sessions, long before spring training.

It's only been nine starts, but Flaherty is pitching his best brand of baseball since 2019 and 2021 when he was with the St. Louis Cardinals. He attributes the success of his fastball and slider to new body movements.

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"It was really about getting the body moving the right way and getting the intent back behind the ball," Flaherty said, "so the intent back behind the fastball, and the slider, we just follow through with that. That was pretty much it. The slider was good pretty much all offseason, and then we made one small adjustment on my grip, and since then, both have been pretty good."

Flaherty, an experienced right-hander who insists there's still room to improve, has a 3.79 ERA with eight walks and 72 strikeouts across 54⅔ innings in nine starts in the 2024 season, his first year with the Tigers. His 3.7% walk rate and 33% strikeout rate are the best marks of his eight-year career. The underlying metrics suggest he's performed even better than his actual ERA, with a 2.92 expected ERA.

He struck out a career-high 14 batters and tied the American League record with seven strikeouts in a row to begin the game in his April 30 start against the Cardinals — his team from 2017-23 — at Comerica Park.

His 35.9% whiff rate ranks No. 1 among qualified MLB starting pitchers, meaning his pitches get the most swings and misses.

"I'm not surprised at all," said catcher Carson Kelly, also Flaherty's catcher in Triple-A Memphis with the Cardinals in 2017. "There's a lot of the same Jack that I caught years ago. When a guy is locating his heater and locating his slider, and then he can drop the curveball as a strike and below, if you have all of those, you're doing something right."

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The whiff rate on his fastball has jumped from 20.8% in 2023 to 28% in 2024, while the whiff rate on his slider has skyrocketed from 26.5% to 42.1%. His curveball whiff rate has improved slightly, from 40.2% to 44.7%.

That's why Flaherty is the best strikeout artist in the AL.

His slider is elite.

"It was a pitch that I didn't have last year," Flaherty said, "but it's been really, really good this year."

Flaherty didn't have a good feel for his slider last season because he struggled to repeat his delivery, and he struggled to repeat his delivery because he wasn't moving his body down the mound the right way. He tried to make adjustments throughout last season, but the problem kept getting worse.

Optimizing the way his body moves through muscle activation was the primary focus of his offseason work. He used to rely on his quadricep muscles to travel down the mound, but now, he focuses on his posterior gluteal muscles and his hamstring muscles.

"I think it's something that has become natural, but it's taken a lot of work," Flaherty said. "I tend to be very quad dominant, and I had to get out of there to get moving the way that I really want to and that makes me the most efficient. Maybe a little bit unnatural just because the amount of work that it takes to continue to do it and repeat it over and over again."

Directionally, Flaherty feels like he is now moving straight to home plate in his delivery.

The velocity on all five of his pitches has ticked up from last season to this season, most notably his fastball from 93.1 mph to 93.8 mph, his slider from 84.2 mph to 85.1 mph, and his curveball from 76.2 mph to 77.8 mph.

"It's allowed me to have a little bit better velo and stay behind the ball and be a little bit more true on my heater," Flaherty said, "and then be able to repeat my slider over and over and throw it a little bit harder. I can just feel the sharpness of it when it leaves my hand, which is something last year I didn't really feel. I felt like it rolled. It never had any bite to it."

With the Tigers, Flaherty is pleased by the consistency in sharpness that he feels for his revived slider, a result of new body movements and an updated grip. He commands his slider along the bottom rail of the strike zone.

"I think it's just everything," Flaherty said. "A little mechanical adjustments that went on this offseason. You see a couple of good ones, and you get the confidence back to throw it whenever. You keep seeing results, and it's something you can keep going to."

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Flaherty has been dominant before.

He finished fourth in National League Cy Young voting for his performance in the 2019 campaign, also finishing 13th in NL MVP voting. That year, Flaherty posted a 2.75 ERA with 55 walks and 231 strikeouts in 196⅔ innings. He also had a 3.22 ERA in 2021, but he was limited to fewer than 80 innings due to left oblique and right shoulder strains. Since then, Flaherty has been searching for the keys to unlock his potential again.

He had a 4.99 ERA in 2023.

In 2024, Flaherty is finally showing signs of his old dominance.

"It's been a good start," Flaherty said. "Still some things to clean up, some pitches I want back, especially some two-strike pitches where I had the chance to put guys away and haven't quite done that. There's progress to be made and things to be improved upon, but it's been fun learning from these guys."

Contact Evan Petzold at epetzold@freepress.com or follow him @EvanPetzold.

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Next up: Royals

Matchup: Tigers (23-24 entering Tuesday) at Kansas City (30-19).

First pitch: 2:10 p.m. Wednesday; Kauffman Stadium, Kansas City, Missouri.

TV/radio: Bally Sports Detroit; WXYT-FM (97.1).

Probable pitchers: Tigers — LHP Tarik Skubal (6-0, 1.80 ERA); Royals — LHP Cole Ragans (3-3, 3.70).

More online: Tuesday's game in Kansas City ended after this edition went to print. Visit freep.com/sports for the game result.

This article originally appeared on Detroit Free Press: Detroit Tigers' Jack Flaherty is starting to look like old self