According to MLB.com, the contract includes incentives such as a $3 million bonus if Imai throws 100 innings in 2026.
Imai, who turns 28 in May, doesn’t fit the prototypical build of a dominant pitcher at 5-foot-11 and 154 pounds, but his production in Japan indicates he could be a front-of-the-rotation pitcher in Major League Baseball. He was a three-time All-Star in Nippon Professional Baseball (NPB) and is coming off the best season of his career.
In 2025 while with the Saitama Seibu Lions, Imai posted a career-best 1.92 ERA en route to a 10–5 record. He had a sub-1.000 WHIP and a career-high of 3.96 strikeouts per walk. Over 163.2 innings, Imai struck out 178 batters while giving up just six home runs. He was also part of a combined no-hitter by the Lions, with Imai throwing the first eight innings before Kaima Taira completed the no-hitter in the ninth.
Over his eight seasons with the Lions, Imai went 58–45, but his record doesn’t do justice to his performance. He had a microscopic 3.15 ERA and averaged nearly a strikeout per inning. He’s posted an ERA of 2.45 or lower in each of the last four seasons and has an impressive and diverse pitching repertoire that should serve him well in the States.
He throws five different pitches, including a four-seam fastball that had an average velocity in 2025 of 94.9 mph, which was just above the MLB average for right-handed starters of 94.6 mph.His main off-speed pitch is his slider, which generated a whiff rate—or the percentage of pitches swung at and missed—of 46 percent last year.
For comparison, just seven pitchers in all of MLB last year had at least a 46 percent whiff rate on their sliders. Imai also throws a changeup, as well as a splitter and curveball. Additionally, he’s shown the stamina to go deep into games and logged five complete games, as well as three shutouts, in his last year in the NPB.
Imai entered the posting system in November and was given until Friday, Jan. 2 to sign with an MLB team. If he wasn’t signed during this timeframe, then he would have reverted back to his prior team in the Lions and wouldn’t have been able to be posted again until next offseason.
A player of Imai’s pedigree and relative youth had many teams interested in his services. The pitcher is represented by super agent Scott Boras, who, shortly after the 2025 MLB season ended, identified the factors that Imai would be attracted to with his first MLB club.
Houston certainly satisfies Imai’s requirements, being the fourth-most populous city in the United States and having been a fixture in the postseason for much of the last decade. Despite missing out on the playoffs in 2025, Houston had made the postseason in each of the previous eight seasons, advancing to seven straight American League Championship Series, making four World Series appearances, and winning two championships.
The Astros signing Imai now gives the team options when it comes to two-time All-Star pitcher, Framber Valdez, who is a free agent. He is one of the most coveted pitchers on the market, and while Houston would love to retain his services, the Astros would only want to do so on their terms. Imai’s signing would lessen the blow if Valdez does end up departing for another team.