It’s been a long, difficult journey for the former Florida Gator college standout, but Jackson Kowar is on track to becoming the best version of himself
The Mariners announced on Wednesday they have activated reliever Jackson Kowar. When Kowar gets into a game for the Mariners, it will be the first time he’s pitched competitively since September 27 of 2023.
Eagle-eyed spring training aficionados might remember Kowar’s Mariners debut in March of 2024: he appeared in two games and threw 12 pitches over two brilliant innings, striking out three and allowing no hits and no walks, and then immediately went on the IL with what would turn out to be a complete UCL reconstruction with the brace procedure.
It was disappointing for Mariners fans excited to see one of the returns of the Jarred Kelenic – Marco Gonzales – Evan White trade, where the Mariners got already-injured pitcher Cole Phillips and Kowar from Atlanta in return for lightening their roster, literally and metaphorically. But it was even more disappointing for Kowar, who was off to the best start of his career after donning a Mariners uniform.
“That was probably the best I’ve ever thrown,” said Kowar about his brief Mariners debut during a lengthy interview conducted on the backfields this spring training. “I was feeling great.”
In 2018, Kansas City had a bounty of first-round picks in the MLB Draft: four in the top 40, more even than the Mariners in their 2023 Draft bonanza. The Royals used those picks on four highly-touted college pitchers, looking to speedily make over a faltering rotation: Brady Singer (18th overall), Jackson Kowar (33rd overall, and teammates with Singer at Florida), Daniel Lynch IV (34th overall), and Kris Bubic (40th overall). Of the four, Singer pitched four solid if unspectacular seasons for the Royals before being flipped to Cincinnati in the Jonathan India trade this past off-season; Bubic is off to a strong start this season after missing most of the 2023-24 seasons with TJ surgery; and Lynch has transitioned to a reliever after struggling with his own shoulder issues. Kowar had the worst numbers out of the crew, struggling wildly with command while failing to miss many bats, and was dealt to Atlanta in the 2023 offseason for an injured Kyle Wright before being dealt again to Seattle two weeks later.
Troy Taormina-Imagn Images
A Fresh Start
Even before he was traded to Seattle, Kowar was dissatisfied with how his professional career had gone, knowing he hadn’t shown his true capabilities as a pitcher yet in the big leagues. After another inconsistent season in 2023, he started training at Tread Athletics, conveniently located in his hometown of Charlotte, when the news came through that he was traded to Seattle—someplace Kowar already knew to be a strong organization for pitching thanks to former organization-mates Gabe Speier and Collin Snider. Tread helped him adjust the shape on his breaking ball, changing his gyro/bullet-spin slider into one with more vertical break—similar to the “deathball” that Jordan Montgomery, who also worked with Tread, made famous during Texas’s World Series run in 2023—that would tunnel better with his other offerings. The Mariners, as is their organizational philosophy, helped him start to embrace the first-pitch strike mentality, encouraging him to have the confidence in his stuff to throw it over the plate. Living at home amongst his support system with a new opportunity on the horizon, Kowar felt like everything was finally lining up for him professionally.
“I changed a lot going into [2024], I had great results, and I really felt like I was on the right track,” he reflected this spring. “Before I got here, I spent a lot of my career, when I struggled, worrying about fixing things I was doing poorly. That was always my messaging to myself: these things I do bad, how do I do them better. I’ve flipped that to, here are the things I do well, how do I make those better, how do I supplement what I do well rather than fix what I do poorly.”
One example: Kowar embraced being a pronation-heavy pitcher, abandoning the supination-heavy pitches he was trying to develop to round out his arsenal. “The idea that you have to have three traditional pitches, I’m happy that’s not really a thing anymore.”
‘Working on a changeup,’ he says, echoing an old scouting cliche and rolling his eyes. “That’s the worst. If he can’t throw one at 21, he’s not gonna pick it up. It’s the narrative: he’s gotta get the third pitch. It’s like, what about a cutter? What about a sweeper? He’s already got a good gyro, what about a four-seamer? What about a seam-shift?”
Previously in his career, Kowar had fallen victim to that working-on-a-changeup narrative. Working with Tread, and then with the Mariners, helped him let go of that obsession with trying to make his worse pitches MLB-caliber.
“The ceiling of those pitches was so low, but I was so obsessed with trying to make bad pitches okay, instead of like, hey, I do these things really well, how do I make that better. So sequencing, where I have the catcher set up, pitch shapes, it’s all been that idea. That’s helped me compete. Like, oh, this isn’t very good, compared to This Is My Best Shit, so let’s make that better. And this a very easy place, this culture, for that to work.”
“I have a huge pronation bias, so me spending time trying to throw good curveballs or sweepers, it’s just not gonna bend my way, which is fine. It doesn’t mean I’m not a good pitcher. Doesn’t mean I’m a failure. Doesn’t mean I can’t do anything. It’s just hey, let’s find some creative way to make a third pitch. So I’m very happy to be in a place like this, where that’s kind of the motto.”
Kowar said it’s been easy to buy in to what the Mariners wanted him to do, especially seeing former teammates Gabe Speier and Collin Snider come to Seattle and find success—and especially in the larger context of the Mariners taking pitchers cast aside by their former organizations and seeing value in them.
“Trent [Thornton] got DFA’d here. Collin [Snider] got DFA’d here. Gabe. It’s just crazy. But then [the Mariners] don’t treat you like you’re expendable. It’s like, yeah, you’re really good, you’re part of the team.”
“It gives you a lot of confidence to get traded here. Like they see something in you, there must be something there. I got so many positive texts when I got traded here, it’s great.”
An Unforeseen Challenge
But then, after his second outing of the spring in 2024, Kowar—who had never missed a game other than a freak accident in the minors where he hurt his toe on a piece of broken bat—felt an unfamiliar soreness that told him something was wrong. An examination revealed a torn UCL, with a recommendation for surgical repair with an internal brace.
After spending significant time overhauling his approach on the mound, Kowar now had to overhaul his mental approach to the game during the long and grueling 14-month recovery period.
“You get so used to, everything in baseball—I enjoy this aspect, because everything’s very black-and-white, it’s very results-oriented, not a lot of gray. It’s numbers and results. Then you have rehab, and all of that’s taken away.
There’s no scoreboard in rehab, there’s no wins and losses, so it’s a lot more about—for me it was trying to switch my brain from being so rewarded by positive results to being more process-oriented. So that’s actually been helpful. I’ve enjoyed trying to make that part of my mental game better, process-wise.”
No pitcher wants to go through the lengthy recovery from TJ surgery, but for Kowar, it offered an opportunity to reset. After enjoying a record-setting career at Florida as the number two starter only because he was teammates with Brady Singer, Kowar—even before the injury—struggled to recapture his form in pro ball.
“I think I spent a lot of my time at the big-league level…too worried about the wrong things. I didn’t always go out there and compete with what I felt was my best stuff. More than anything, even more than the results, that’s what was frustrating. I don’t think I always went out there and showed the best of my arsenal. I was like, oh, this hitter can’t hit a breaking ball, I have to throw a breaking ball even though it’s my worst pitch. I tried to mold too much to my surroundings instead of using what got me there.”
“I think I got hung up on those negative results a little too much in the past, because I was like, I know I’m really good, I know I’m way better than this. I would get so frustrated at my lack of results, it was taking up too much of my brainpower.”
With the Mariners, who have a starting rotation that varies from a fifth-overall pick to a fifth-rounder to a twelfth-rounder and a bullpen that consists of players largely picked up on the waiver wire or in trades, Kowar was able to shake the baggage that came with being an underperforming high draft pick, which comes back to how the Mariners value each of their pitchers equally. “Every single person here believes they have the same shot at the big leagues,” he marvels.
Security and Curiosity
Even while facing the new challenge of rehab from a serious injury while simultaneously learning a new organization, Kowar never felt like the odd man out in the pitching group, saying the Mariners always made him feel included and like he was “rowing in the same direction” as the rest of the team, even while he was on the shelf.
“The best way I can describe it is this is the most secure culture I’ve ever been around in a baseball setting. Everyone really believes that they’re really good. This game can breed insecurities in just about anyone, and that can manifest itself in, the environment just isn’t conducive for everyone trying to get better. People here are really rooting for you, because they’re not afraid you’re going to take their job, because they know they’re good. Everyone knows they’re really good.”
“There’s not filler players here. That is uncommon. And that speaks to, it’s such an easy place to get better, because they’ve empowered every person from the first pick to the twentieth pick to be the best version of themselves. It’s not like you’re just here to fill a spot. It’s not like there are all second overall picks that are in the big leagues here and then free agents. It’s literally homegrown guys that are picked anywhere in the draft. And they’ve had success with high first rounders and everyone in between. It’s just super healthy.”
While he couldn’t pitch, Kowar made sure he could learn everything he could from his new surroundings, throwing himself into the Mariners’ culture. He immediately clicked with the pitching development staff.
“Trent [Blank] and Woody [Pete Woodworth] do a really good job of taking what could be complex ideas and funneling them down into what makes sense for you as a pitcher. There are always going to be guys who want a ton of information, and guys who don’t want any, and they do a nice job of being the filter for you, getting to know you and then cutting the information as slim as you want it to be cut down.”
He connected with his teammates, as well, joining in with the rest of the pitching staff packing in behind the complex wall in Peoria to watch everyone throw bullpens. He picked other pitchers’ brains and studied them, nourishing a long-dormant sense of creativity and curiosity.
“Everyone’s curious in a really good way. They really are rooting for each other, and they want to see what everyone’s doing. People aren’t out there worrying about their roster spots or who’s gonna make the team. It’s like, let’s go watch these people be really good at their jobs. And I think that’s a pretty cool and rare thing in baseball…There’s a lot of competition, but it’s super-friendly, because it’s not like I’m scared for you to beat me out. It’s like we’re all going to be really good. You’d be surprised, that’s not always the case.”
“It’s just a really healthy environment. I’ve loved being a part of it. I’m getting antsy to be a real part of it,” Kowar said this spring, looking longingly towards the back fields in Peoria.
A New Sense of Self
Flattening out the draft curve has helped Kowar appreciate what he’s done well, and what he could have done better to get his big-league career off to a better start. And while he’s somewhat regretful, he’s not at all resentful about how he’s gotten to that place.
“I would love to sit here and say the Royals didn’t do a good enough job developing me, but at the end of the day, I think I was probably needing to be more curious. It’s unfortunate that it took me a couple of bad big-league seasons, but looking back, it was less about where I got drafted, and a lot more that I had a false sense of confidence, where I knew I wasn’t quite where I needed to be, but I was getting results. And I wasn’t quite curious enough to explore making myself a little bit better. So for me, if I’m getting real introspective, I think that’s where I had the most issues, and I’m not sure who would have taken me where that would have been different.”
What does that look like on the granular level, being curious? In response, Kowar, in a solid, uninterrupted monologue of five minutes, easily reels off lists of pitchers and analyzes them: what they do, what they’ve done to be better, how much vertical drop each has, what they get out of their pitch mixes, how their arm moves, if they’re supinators or pronators. Rehabbing from a UCL tear, it turns out, gives you a lot of time to study, especially when possessed of the natural desire to learn and analyze that Kowar has. Listening to him, it’s hard to imagine him ever not being curious, but as he says, his early success made it easy for him to not question his results.
“The last couple of years have led me down a path where I’ve been more curious. It’s tough, because I had a lot of success when I was young and I was just so confident, I didn’t think I needed to learn anything. I was like, I’m bad, I’m nasty. I had built up this version of who I thought I was, but then that wasn’t really working out.”
“This has been a great place to be because curiosity is not a bad thing here. At the end of the day, I feel like it all works out for a reason. I’m in a great spot here.”
Scoreless 7th inning by Jackson Kowar. Fastball topped out at 98.4. pic.twitter.com/mXPezdTQeI
— Mariners Minors (@MiLBMariners) May 15, 2025
Kowar has been working his way back since early May, climbing the ladder from the ACL to Tacoma until now, as he stands poised to throw his first big-league pitches for his new organization. But he admits it will take a little while before he shakes off the feeling like he’s still mired at the complex in Peoria, having to go back and do rehab, looking longingly out where the healthy pitchers are completing their bullpens.
“It’s nice, I get to walk out to the bullpen today,” he said pregame, looking across the field at T-Mobile Park, his new home. “I’m really excited. I’m really going to be grateful for it. When I was younger in my career, you first get called up, you think that’s how it’s always going to be, so I’m going to be very grateful. I’m very lucky to be able to do this. So I’m probably going to take a moment.”
“And then as soon as I sit down, I’m going to start chopping it up with the guys, like I’m right back at home.”