How Will Roki Sasaki Fare in the MLB?

Photo Credit: AP

23-year-old Japanese phenom Roki Sasaki, a star pitcher for the Chiba Lotte Marines in Nippon Professional Baseball (NPB), has officially been posted for MLB teams to sign. Sasaki is set to become the most cost-effective elite starting pitcher available this offseason due to his international amateur status. Being under 25, he must sign a rookie deal that pays the MLB minimum for three seasons, followed by three years of arbitration before reaching unrestricted free agency—mirroring Shohei Ohtani’s early MLB trajectory.

Last offseason, Yoshinobu Yamamoto was posted and signed by the Dodgers. As some may recall, I did an analysis back then aiming to predict how Yamamoto would fare in the world’s best baseball league. Using that same logic, but adding Yamamoto’s predicted and actual data to my dataset for the model, how is Sasaki projected to perform in the MLB?

Let’s start by reviewing my Yamamoto projections. His NPB average, my 2024 MLB prediction, and his actual results are shown in Table 1 below.

Table 1: Yamamoto’s 3-season NPB average, Paraball’s 2024 MLB prediction for him based on the historical statistics of Yu Darvish and Masahiro Tanaka, and Yamamoto’s actual 2024 results 

As we can see, my predictions were pretty spot on for the star righty’s ERA and strikeouts per nine innings pitched (SO9). I did, however, come in high on innings pitched (IP), mostly because Yamamoto faced a shoulder injury that severely limited his season. Moreoever, my projections underestimated his walks and hits per inning pitched (WHIP) and hits allowed per nine innings (H9), while overestimating his home runs allowed (HR9) and walks (BB9). Overall, my predictions aligned more closely with his actual performance than his NPB statistics, suggesting that the approach is on the right track. With Yamamoto’s data now incorporated into my dataset, my hope is to make even more precise predictions for Sasaki.

Let’s see what the model says.

Projections for Sasaki’s MLB Performance

My model’s projections for Sasaki are shown in Table 2 below.

Table 2: Sasaki’s 3-season average in NPB and his MLB projections based on historical data from Yu Darvish, Masahiro Tanaka, and Yoshinobu Yamamoto 

The model’s projections are not too kind to Sasaki. This is primarily due to his higher ERA and walk rate in the NPB compared to his Japanese peers, as well as his home run rate, which is tied for the highest in the group. That said, I’d caution against reading too much into the ERA projection, given the variability introduced by non-pitching factors.

Sasaki is forecasted to outperform Yamamoto's 2024 numbers in key metrics like WHIP, H9, and SO9, though he’s projected to lag in HR9, BB9, and SO/W. The most notable projection, however, is his limited workload—just 87.1 innings pitched—fewer than Yamamoto’s actual IP for the 2024 season.

This suggests Sasaki could be deployed similarly to Yamamoto, taking on a reduced regular-season role while serving as a critical playoff asset. Alternatively, he could thrive as a highly valuable multi-inning reliever if his new team opts for that approach.

Not surprisingly, the Dodgers are considered heavy favorites to acquire Sasaki. Let’s see where this young talent ends up!