Shota Imanaga Isn't Just Good - He's Historically Good
From the shadows of his star countryman, Imanaga is re-writing the record books
It wasn’t supposed to be this way. In the duo of high-profile Japanese pitchers that came to the MLB this past offseason, Imanaga was supposed to take the back seat to superstar Yoshinobu Yamamoto. Yamamoto, who signed with the Dodgers on a gargantuan contract of 12 years, $325 million (plus a $50 million signing bonus), was the jackpot.1 Imanaga, who signed with the Chicago Cubs, was merely seen as the consolation prize. Nobody can be faulted for thinking this, Yamamoto was coming off three-straight Japanese Pacific League MVP awards and a trio of Eiji Sawamura Awards (essentially the Japanese equivalent to the Cy Young, but arguably more difficult to attain). Imanaga was not a slouch by any stretch. In eight seasons with the Yokohama BayStars, he went 64-50 with a 3.18 ERA and 1,021 strikeouts.2 He was good, just not nearly “Yamamoto good”. Now however, Shota Imanaga is making us question who the real star is, and he is doing so in historically great fashion.
A Historically Good Rookie
Shota Imanaga is pitching like no “rookie” we have ever seen before. I use the word rookie loosely, as he is technically a seasoned professional ballplayer. Although he played for eight years in Japan before joining the Cubs, in the eyes of the MLB he is a rookie. Regardless, through 9 starts this season he is pitching better than any first-year player in the MLB in the “Live Ball Era” (since 1920). His 0.84 ERA is nearly half that of the next-best rookie pitcher in their first 9 starts. The table below shows the top rookies by ERA through 9 starts.
Historically Good…PERIOD
Imanaga’s season so far does not just stand out amongst rookies, it stands out amongst all pitchers. Below is a table of the lowest ERAs of any pitcher in the Live Ball Era.
Digging a little deeper, Imanaga is generating Wins Above Replacement (WAR) at a higher rate than any pitcher since 1920. The table below consist of the top-25 pitchers by WAR through 9 starts and their WAR per 9 innings pitched (WAR/9).
Only Leon Day of the Negro League’s Newark Eagles in 1942 generated more total WAR through 9 starts than Imanaga, and nobody has generated more WAR/9 IP. Slight digression, but I can’t help but notice the disproportionate number of pitchers in this 2024 season that wound up on that list. That will likely be a story in and of itself at a later date. The discrepancy between Imanaga and the rest of the best pitchers through 9 starts is exemplified when looking at ERA and WAR/9 in tandem.
We are truly seeing something special from Imanaga, and we’ve never seen anything like it in modern Baseball.
Can He Keep It Up?
Needless to say, it would be shocking to think so. While I would love to see this incredible run continue, the realist and statistician in me knows that some regression to the mean is quite likely. Below, we see a comparison of his current stats against his expected stats from Statcast and FanGraphs3.
All signs point to some fairly substantial regression for Imanaga. Regardless, his expected stats are all quite good, just not quite up to the caliber that his is performing now. IF in fact he can keep it up, his 0.84 ERA would rank 3rd all-time in the Live ball Era, behind only Robert Keyes and Roy Parnell; two Negro League pitchers from 1944 and 1932 respectively.4 Assuming Imanaga stays healthy and pitches at the rate he has thus far, his current WAR of 3.0 projects out to 10.1 over the course of the full season.5 This would put him in a tie with Randy Johnson for 28th all-time, and tied for 4th best since 2000.6 While it is very unlikely we will see this dominance continue, it is fascinating to imagine the possibilities and appreciate what we are seeing right now.
Imanaga vs. Yamamoto
As I discussed at the start, Yoshinobu Yamamoto was supposed to be the star, with Imanaga taking the back seat in this past off-season’s free agency. He was like the opening act of the Yamamoto concert - nice to have, but not what you really came for. Oh, how quickly things can change. Below is a comparison of Imanaga versus Yamamoto who, as I write this, have both pitched in and started 9 games. In parentheses is how each player ranks in the majors in that stat.
Yamamoto was scheduled to take the mound last night against the Arizona Diamondbacks for his 10th start, so his overall stats have likely changed, but both players’ stats through just 9 games are set in stone. I would have liked to get this piece out earlier, well before Yamamoto pitched his 10th game, but unfortunately I don’t write on Substack for a living, and there are only so many hours in the day…I do my best, folks. Nevertheless, it is clear who the real catch has been thus far between the two star pitchers. Only time will tell if Imanaga will continue to outshine his countryman, and lucky for us, all indications are that we have a lot of time left with these two great phenomenal players.
FIP and BABIP data via FanGraphs. All other stats via Statcast.
Major League Leaderboards - 1920 to 2024 - Pitching | FanGraphs Baseball
Current WAR from Baseball Reference
Player Pitching Season & Career Stats Finder - Baseball | Stathead.com