It was his third bullpen in last year's spring training.

Detroit Tigers right-hander Jackson Jobe felt a sharp pain in his back on one of his throws. He was diagnosed by the Tigers with lumbar spine inflammation and sidelined for the first two months of last season.

Trying to throw a faster fastball led to his back injury.

Jobe, whose fastball maxes out at 99 mph, recovered from the back injury and dominated on the mound in the 2023 season, thanks to better fastball, new cutter, nasty changeup, tweaked slider and refined command. He is primed for another breakout — maybe even his MLB debut — in 2024 for all of those reasons, as well as his maturity.

"You think you're invincible in a way," Jobe said. "I thought something like that would never happen to me, then it did. It was a wake-up call for me. I learned how to take care of my body and keep from something like that happening again. ... I've made some adjustments from that to try to be a little safer."

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Entering 2024, Jobe is healthy and ready for his first taste of big-league spring training with the Tigers. Alex Marney, founder of PitchingWRX, has high expectations after spending another offseason training Jobe in Oklahoma City, Oklahoma.

"If he goes out and does the things that he does," Marney said, "and if he proves he can stay healthy, I don't know how you could not see him potentially being up there in the second half of the year. He's just that talented, and his stuff is just that good. I think he showed that when he's on, it plays at all levels."

Rehabbing from the non-surgical back injury meant Jobe couldn't pitch in a competitive game until the Tigers cleared him in June 2023 for the Florida Complex League.

He pitched like an elite prospect in his return, posting a a 2.82 ERA with 11 walks (3.4% walk rate) and 103 strikeouts (31.7% strikeout rate) across 79⅔ innings in 20 starts, including one start in Double-A Erie and four starts in the Arizona Fall League.

"He has dominating stuff," said Tigers president of baseball operations Scott Harris, who ultimately decides when Jobe climbs the mound in Detroit. "The most important thing for him is he made a real adjustment from Lakeland to West Michigan, where he started absolutely challenging hitters and realizing how good his stuff is. When he was throwing chase pitches, he was often doing hitters a favor, so he started challenging them directly by landing all of his shapes in the zone repeatedly and ending at-bats quickly, which allowed him to go deeper in games. That's going to be a very valuable skill when he gets to the big leagues."

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Jobe is one of the best pitching prospects in baseball, just 30 months after the Tigers (under then-general manager Al Avila) selected him No. 3 overall — one pick before the Boston Red Sox took shortstop Marcelo Mayer — in the 2021 draft out of high school.

A lot has changed since his draft year.

"It's pretty night and day," Jobe said. "There's way more thought behind it now. It's kind of a chess match, like being able to tell if guys are sitting on sliders or being able to fool guys. I plan on playing for a while, but it's definitely cool to see how far I've come, even just the thought process from one year to the next."

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Developing a four-pitch mix

Coaches with the Tigers told Jobe to move to the third-base side of the mound in the Arizona Fall League, an adjustment that took Reese Olson's fastball to new levels on his way to a big-league breakthrough.

The Tigers moved Jobe to the third-base side to create deception to help his high-velocity four-seam fastball perform better against upper-level hitters. His first start was on the middle of the mound; his final three starts were on the third-base side of the mound.

"He was pretty extreme on the first-base side of the rubber," Marney said.

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Jobe maintained the perceived ride on his fastball, which he has been working on since the his first bullpen in the Tigers' organization by staying behind the ball through his release, while his in-zone whiff rate jumped from 21.5% in the regular season to 44.7% in the Fall League.

He also learned where to locate his 96 mph fastball.

"To righties and lefties, my fastball played worse when I was throwing it middle-in," Jobe said. "Being able to pound fastballs down and away to righties helps the slider play better and all that stuff, so it was a lot that I learned. I'm really staying away from middle-in. That's the damage zone with my fastball."

The slider still grades as the best pitch in Jobe's arsenal, and the slider misses bats at an elite rate, but opponents adjusted to his big slider by eliminating the pitch in games, so much so that Jobe had to adjust back by tightening his slider — creating a sweeper movement — to induce more swings.

That's also why the Tigers instructed Jobe to insert a cutter into his pitch mix.

He didn't throw his 91 mph cutter as often as his three other pitchers in the regular season, but it was the easiest secondary pitch for him to locate in the strike zone.

"The cutter helps the fastball and slider," said Ryan Garko, the Tigers' vice president of player development. "We added a pitch between the two of them, and it gives the hitters a different look. Don't know if it's a slider of a fastball, and it ends up being a cutter."

Look for the bigger slider that propelled Jobe to the top of draft boards, rather than the sweeping slider, in the upcoming season because of his move to the third-base side of the mound.

His slider averaged 3,050 rpm last season.

"He's going to have something with a little bit more depth," Marney said, "and it can be a little bit bigger from over there. I think you'll see it return to its normal action this year."

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The changeup gave opposing hitters the most trouble last season, with a 50.8% whiff rate. Changeups to right-handed hitters became the X-factor in his attack plan as the complement to sliders down and away and fastballs up in the zone.

"It's hard (for hitters) to cover all three locations," Jobe said.

But Jobe rarely threw the changeup in high school. He worked on his changeup with Marney at PitchWRX in the offseason after the 2021 draft and before the 2022 season.

The development of Jobe's changeup started with a generic split-changeup grip that a college-aged Marney learned from Brent Strom, currently the pitching coach for the Arizona Diamondbacks, about 15 years ago.

"It was a grip that Brent Strom showed me," Marney said. "That's where we started with Jackson. He has such a good feel for what he's trying to do with it, so the grip became a little bit more modified because he made it his own. The rest is history."

The changeup was a fine third-best pitch in 2022, but Gabe Ribas, the Tigers' director of pitching, recommended Jobe throw more right-on-right changeups in 2023.

Listening to Ribas' advice resulted in more strikeouts because Jobe wasn't as predictable against right-handed hitters.

"If guys want to sit there and hunt the slider, then I'll throw the changeup," Jobe said. "If they get more ready for the changeup, then I'll throw the slider. I think the slider and the changeup play really well off each other, and then being able to throw hard at the top of the zone, they have a lot to be thinking about."

"The changeup is disgusting," Marney said.

'Some of this is him growing up'

Just recently, Jobe reached back for his first maximum effort throws of the 2024 season. He only threw a few max-effort fastballs in a touch-and-feel bullpen as a precursor to his first full-throttle bullpen. The final throw was his fastest pitch since the Fall League.

The TrackMan device calculated the velocity.

It showed 96.9 mph.

"You want another one?" Marney asked.

"Nope," Jobe responded. "I'm saving my bullets."

In previous years, a velocity-hungry Jobe might not have responded that way, but the kid growing into a man learned from the mistakes of last year's back injury, just like he learned on the mound. These days, his ability to make adjustments stands out to his coaches.

Maturity is one reason for Jobe's development.

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He was drafted at age 18; he's now 21 going on 22. He feels strong and aware of his body. He went from knowing a little bit about advanced analytics to knowing everything about advanced analytics. He leveled up from a thrower to a pitcher in two minor-league seasons.

"Everyone wants to rush to some judgments for a 19-year-old in the Florida State League," Garko said. "Some of this is him growing up. You see a picture from the first spring training to the second, and he doesn't even look like the same person."

His command looks different, too.

He averaged 0.8 walks per nine innings in the regular season and 2.9 walks per nine in the Fall League in 2023, a significant improvement from 3.5 walks per nine in 2022.

The better results, as a product of the work, allowed Jobe to receive national recognition. He is ranked No. 10 by ESPN (previously unranked), No. 20 by Baseball America (previously at 83) and No. 25 on MLB Pipeline (previously at 63) on the preseason top-100 prospect lists. Only a few other guys are in the mix for best pitching prospect.

This one could soon be ready for his MLB debut.

"It's easy to say I want to be at this level or that level," Jobe said, "but a lot of times, that's out of our control, so I think the biggest thing for me is pitching a whole season. I want to have success, throw over 100 innings and prove I can stay healthy over the course of the season."

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

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This article originally appeared on Detroit Free Press: How Detroit Tigers' Jackson Jobe developed into top pitching prospect