Meanwhile, the Lions will receive postal compensation based on Imai’s $54 million guarantee. The current international posting system gives the originating club 20% of the first $25 million, 17.5% of the next $25 million and 15% of anything over $50 million. That amounts to $9.975 million, so the Astros are on the hook for just under $64 million between the contract’s guaranteed money and postal costs. If Imai opts out next season, Houston has committed $27.975 million for one year of his services. The Astros would also owe the Lions a 15% postage fee on any escalators Imai unlocks if he doesn’t opt out.
Imai was one of the best starters available in free agency, coming off a career-best 1.92 ERA season with the Saitama Seibu Lions of Japan’s Nippon Professional Baseball. Just days ago, it was reported that he had met with teams in person ahead of his January 2 signing deadline. The Yankees, Mets, Cubs, Phillies and Orioles were among the clubs interested in signing him, so the Astros are a bit of a surprise destination.
We at MLBTR ranked Imai No. 7 on our Top 50 Free Agents list and projected him for a six-year, $150 million contract. This deal with Houston ends up being half the length of that projection, with about a third of the money guaranteed. It seemed like Imai had other offers on the table for longer terms, but lower AAVs (link via Mark Feinsand of MLB.com). The opt-outs in his deal with Houston allow him to try to get a bigger contract in future offseasons if he can prove himself in the MLB.
Imai is 27 years old (28 in May) and has pitched a 3.15 ERA in 963 2/3 NPB innings in his career. He debuted in 2018 at age 20 and made 16 appearances (15 starts), but struggled with a 4.97 ERA. Those early struggles lasted from 2019 to 2020. In the pandemic season, Imai had a 6.13 ERA in 61 2/3 innings and walked more than he struck out, which led to him being temporarily moved to the bullpen. He bounced back in 2021, posting a 3.30 ERA in 158 1/3 innings with an improved strikeout rate, and has since stuck around as the starting pitcher.
That was the start of a period of dominance from 2022 to 2025. After a 2.41 ERA in nine starts with the Lions in 2022, Imai followed with a 2.30 ERA and a 24.4% strikeout rate in 133 innings in 2023. Although he walked 11.4% of batters faced that year, his strikeout and walk numbers improved year over year from 2023-25. This year, he struck out 27.8% of batters (the highest among qualified NPB starters) and walked just 7.0%. His K-BB rate of 20.7% was third best in that league. Imai also did very well at keeping the ball in the yard, allowing just six home runs all season (0.33 HR/9) and inducing groundballs 48.3% of the time. Overall, he heads to the majors with a higher ceiling and much better control compared to his early career.
Things-wise, Imai profiles as a mid-rotation starter in the majors. His fastball is in the mid-90s and can reach 99 mph, and he also throws a slider, splitter and changeup. His stellar performance from 2022-2025 made him an attractive target in free agency, though some evaluators were concerned about his secondary and past struggles with control. It seemed like industry opinion was divided on whether he could succeed as a big league starter, which resulted in the lower-than-expected guarantee.
At the time he posted this, a $150 million deal seemed like a real possibility. Nowadays, teams value youth and edge and are willing to pay a premium to get it. Recent offseasons have seen players like Juan Soto And Vladimir Guerrero Jr. sign for more than a decade and at least $500 million in guaranteed money. Among Japanese players, right-handed Yoshinobu Yamamoto and outfielder Junghoo Lee came to the majors after their age 24 season and earned deals in excess of $100 million. Imai is several years older than Yamamoto when he signed and has a shorter track record as a front-of-the-rotation arm. While he could never match Yamamoto’s deal, Imai’s year-over-year improvement and relative youth were enough for the Astros to want him in their rotation.
Houston’s interest wasn’t widely known, although it makes sense that they wanted another starting pitcher. Old ace Framber Valdez is currently a free agent. The team has had some discussions with Valdez’s camp, although the expectation is that he will sign a more expensive contract elsewhere. Hunter Brown was phenomenal in 2025, totaling 185 1/3 innings and an ERA of 2.43. That mark was third-best among qualified starters, behind only Cy Young winners Paul Skenes And Pull Skubal. He also posted an 85th percentile strikeout rate and a 77th percentile groundball rate. Overall, he was worth 4.6 fWAR and finished third in the AL Cy Young voting. He will return as top staff member in 2026.
Behind Brown, the rotation looks shaky. Christian Javier currently projects as the No. 2 starter. He owns a 3.66 ERA in 538 career innings, but he only threw 71 2/3 innings from 2024 to 2025 due to Tommy John surgery. In just 37 innings this year, Javier had a 4.62 ERA with a 21.7% strikeout rate and a 9.6% walk rate. He is under contract until 2027. In the meantime Lance McCullers Jr. has had his own injury problems, throwing just 103 innings in the past four year and missed 2023-24 entirely. Even if he performs well in 2026, the team will keep a close eye on his workload. The recently acquired Mike Burrows will play a role. He had a 3.94 ERA in 96 innings this year with an impressive 16.4% K-BB rate, though his overall track record is fairly minimal.
The addition of Imai gives the Astros a durable No. 2 or 3 starter at an affordable price. It remains to be seen how his strikeout and groundball potential will translate to Major League hitting, though the club certainly hopes he can maintain his performance from Japan. The signing brings the Astros’ projected payroll to $242 million Grid source. The club was a luxury taxpayer for the second time this year and hopes to avoid having to do so for the third time. The initial luxury tax threshold for 2026 is $244 million, so the club will likely have to cut payroll if it wants to add to other parts of the roster.
Now that Imai is no longer on the board, clubs in need of a starter will have to look elsewhere. Dylan stops was the top free agent pitcher entering the offseason and has since signed with the Blue Jays. Valdez, Ranger Suarez, Zac Gallen, Chris BassittAnd Luke Giolito are still available in free agency. Valdez and Suarez are rotation options, while Gallen, Bassitt and Giolito are cheaper mid-rotation arms.
Jon Heyman of The New York Post first reported that the Astros and Imai had reached a deal. ESPN’s Jesse Rogers was the first in the three-year term with opt-outs after the first two seasons. Heyman reported the $54 million guarantee and $9 million in escalators at 80-100 innings, while Ronald Blum of Associated Press was first on the signing bonus and the specific escalator malfunction.
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