How Good is Tatsuya Imai? | NPB Player Profile

Yuri Karasawa (https://x.com/yakyucosmo) breaks down Saitama Seibu Lions right-hander Tatsuya Imai, who has been posted to MLB this offseason.

Murakami video: https://youtu.be/FN1ACMov6po
Okamoto video: https://youtu.be/fMZBoO_96Z4

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00:00 – Introduction
00:13 – Progression
02:30 – 2025 Season
03:26 – Career Stats
04:02 – Pitch Mix Breakdown
06:09 – Player Comps
06:37 – Concerns
07:26 – Overview & Conclusion

Saitama Lions ace Tatia Imi is headed to Major League Baseball via the posting system. So who exactly is Imi? How good is he? And what should his expectations be as he transitions to playing in North America? Flashback to almost a decade ago and the Toigi native was one of the better high school talents in the nation, helping Samra in Japan to the 2016 U8 World Cup title, leading to his selection by Sabu in the first round of the MPB draft. He made his big league debut in 2018 and picks out of the rotation with mostly below average results for several seasons partially due to his inexperience command issues and a few smaller injuries. However, 2021 would be his breakthrough as the right-hander was a firsttime all-star after throwing 158 innings with a 3.30 erra. He even beat Yoshinobu Yamamoto in a head-to-head matchup on May 5th and set a career-high with 13 strikeouts in a complete game shutout on September 11th. He only made nine starts in 2022 due to various health issues including a leg injury, ankle sprain, and tonsillitis, but he had a lot of success over a small sample, posting a 2.41 ERA and 25% strikeout rate. His 2023 campaign had some major ups and downs in the early going. He had an 11 strikeout complete game shutout on April 13th. He threw six no hit innings while walking seven batters on April 28th. And then he had one of the worst starts of his career with eight earned runs in two plus innings on May 24th. A start I remember because I happened to be at the game that day, leading to a temporary minor league assignment in June. Well, that seemed to light a fire under him as he hurled eight innings of one-run ball in his first start back and he really hit the ground running from there and finished with a 1.41 erra over his final 12 starts. And I think that was really around the time that I finally found some consistency as he took that momentum right into 2024, posting a career best 173 innings while maintaining a 2.34 ERA, which is good for a 125 ERA plus in the dead ball environment. Now, his control of the strike zone still wasn’t great. He had three walks or more in over half his starts, but it was the lowest walk rate of his career at 10% and he was able to lead qualified pitchers with a 26% K rate. So this effectively wild approach was very much working for him. But then we get to 2025 and this is when I truly puts it all together as he took a sub one erra into the month of June. His most memorable start from early in the season came on April 18th when he threw eight no hit innings, greatly contributing to his team’s combined no hitter. He even had 16 consecutive quality starts dating back from August 24th of last year until June 7th, a new level of consistency we really hadn’t seen from him before. Then came the most dominant outing of his life. On June 17th, he fired a two hit complete game shut out on 123 pitches with 27 whiffs and 17 strikeouts, breaking Dice game Matsuzaka’s single game franchise record. But actually, what stood out to me most about this historic start wasn’t the 17 strikeouts. It was that he didn’t walk a single batter. And that sort of symbolizes Imi’s evolution as a pitcher as he finished 2025 with a career best 7% walk rate and 66% strike rate following a trend of him improving that strike throwing ability each and every year. Now he struggled a bit in July but otherwise was excellent ending his campaign with a 1.92 RA or a 156 RA plus over 163 and 2/3 innings. He was pretty definitively a top two or top three starter in MPB, leading all qualifiers with a 28% strikeout rate and 16% swinging strike rate. But what exactly is Imi doing as a pitcher to achieve these results? Well, the 27-year-old is a bit unorthodox to say the least. When facing same-handed opposition, Imi relies on his forcing fast ball and slider 93% of the time, and he absolutely obliterates them with a 32% K rate and 173 opponent average versus righties since 2024. And the reason he can be such an effective two- pitch guy is because his fastball sits 95 plus miles per hour from a lower release height and arm angle. And his slider features a very unique tight movement profile, often with armside break, making it more of a reverse slider or gyro ball. It had a goddy 53% whiff rate against righties. And he really consciously changed the shape of this pitch a few seasons ago because it tunnels better with the fast ball compared to say a more traditional slider or sweeper. The fastball shape isn’t elite by any means, but again, he sits 95 to 96. He can run it up to 98.99 in high leverage situations and the armside run going into righties is just highly effective from his release point. Against lefties though, Emi has to diversify and dealing with those platoon splits was a clear weakness in his past seasons. But he made big strides in his other secondaries in 2025, mixing in a change up splitter and a new Vulcan change late in the year, which he refers to as a sinker because he learned it from his teammate Riyotaa. Uh he used those three off-speed weapons plus his curveball a combined 29% of the time against left-handers in 2025 and that helped him get to a career best 25% strikeout rate and 180 opponent batting average. In fact, this was his first time ever posting an X-Fip minus better than league average versus opposite hand hitters. So, with a reliable fastball slider combo to righties, newfound success to lefties, overall improved locations, and a full healthy year, it’s no wonder that Emi was able to have a career season. When you consider player comps, you can make a lot of parallels to Luis Castillo, who has a lot of these similar shapes, including that unorthodox gyro slider. For a higher upside comp, perhaps Joe Ryan is whom I could model his game after. And I’d even throw out Trey Savage, who is so different in terms of the high slot and high-ride fastball, but does have the same characteristics when it comes to that very unique armside slider. Now, my main concerns for Imi in MLB are whether his change up and splitter will consistently neutralize lefties, at least as ground ball pitches, and how steady his command will be if he needs to pitch out of a fiveman rotation instead of a six-man. Having a great framer behind the plate would obviously help with this. And then whether controlling the running game will become a liability. He allowed the most stolen bases in MPB this past year in large part because he really wasn’t focused on holding runners. That said, you can tell that I has made not just subtle but pretty noticeable changes throughout his entire career, especially mechanically. I think he’s really open to tweaking things, thinking about his strengths and weaknesses as a player, and he’s always looking for what will give him the competitive edge. I think an MLB organization that gives him the runway to grow into a frontline starter, maybe even one of the faces of the franchise while still helping him refine these smaller parts of his game. Maybe adding in a sweeper or a hard sinker, maybe lowering the arm slot even more would be the ideal landing spot for him. His floor is certainly lower than some others because the command is average at best and the arsenal isn’t as deep as, you know, Yoshinobi Yamamoto, but I think his ceiling is like a more durable version of Kodai Sena, a potential number two in the rotation. So, I’m really excited to see where he goes and I wish him all the luck in Major League Baseball. Thanks for watching. This has been Yuri Carasawa with Japanball.com. Make sure to check out all of Japan Ball socials on X, Facebook, and Instagram for news, updates, and analysis on Japanese baseball. Also, check out extrainings.com for information on international baseball tours, including to Japan.