Evaluating international free agent RHP Kodai Senga

When Shohei Ohtani was posted after the 2017 season, he was rightfully viewed as having the best fastball among NPB starting pitchers, and it wasn’t particularly close. His slider was tops among starters too. But some scouts didn’t think his splitter — which has become his top off-speed offering in MLB — was the best among his peers. That honor belonged to Kodai Senga.

Earlier that year, Senga gained attention while pitching in the World Baseball Classic. He was already known as one of the best starting pitchers in Japan, but due to a preponderance of top arms in Japan’s rotation, he moved to the bullpen where his stuff took an electric step forward. In Japan’s semi-final game against the US, Senga allowed the winning run in relief but also struck out five MLB batters in two innings pitched. Senga’s WBC prowess created a lot of buzz among scouts in Tokyo (some of whom were getting a good look at him for the first time), and it cemented his place on MLB teams’ radars.

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More than five years later, Senga is finally available for MLB teams to sign as an international free agent, delayed by several years due to the Hawks’ philosophical opposition to using the posting system. This means that Senga is a few years older than the typical pitcher coming from Japan (he turns 30 in January) but he will not require a posting fee to sign and he is eligible to negotiate with all MLB teams simultaneously. Senga’s MLB dreams have been documented for quite a while, but his long career in Japan has resulted in many pitching accolades and five Japan Series championships.

While the delay due to the Hawks’ refusal to post him has meant that more of Senga’s prime was spent in NPB, the timing of his free agency is still good for him, as he is coming off one of his best seasons. Senga’s 144 innings is the most he’s thrown since 2019 (more on that later), and his 1.94 ERA was a career-best. He also posted career-best marks in swinging strike and contact rates. In his 22 starts, Senga struck out 27% of the batters he faced, second only to phenom Roki Sasaki among pitchers with at least 120 innings in NPB.

Senga relies primarily on a four-pitch mix. His 96.0 mph average four-seam fastball velocity (per Japanese baseball data aggregation site DeltaGraphs) in 2022 was the highest of his career, and he touched 101 mph in a start against the Fighters in May. Senga’s fastball also features some natural tailing action due to his three-quarters arm slot, enough to keep it away from left-handed batters’ barrels at times. Despite the elite (for NPB) velocity and good movement, the results against Senga’s four-seamer have been relatively ordinary, as his ability to command the pitch can waver. Instead, it serves to set up his other pitches, all of which profile as above-average offerings.

Senga’s primary off-speed weapon is his elite splitter, with the equally elite nickname “ghost fork,” named such because it completely disappears. According to Jim Allen’s profile of Senga, that splitter was the hardest pitch to make contact with in all of NPB last season. It would be his primary late-count weapon in MLB as well, and there is very little doubt that it can continue to miss bats no matter where he pitches.

Senga also features an above-average cutter-slider combo. The former lost some velocity in 2022, averaging 88 mph, serving almost as a hard slider. Senga also throws a softer slider which averages around 83 mph with slurvy break. Both pitches miss a lot of bats as well:

Senga can also mix in an occasional show-me curve and a two-seamer, which added up to around 5% of his pitches in 2022. Neither pitch profiles as well as his four main offerings, but they do give Senga six total pitches to work with.

While Senga’s tools are about as sky-high as a team can find on the open market this offseason, they do not come without some potential pitfalls. Senga can struggle with wildness at times, posting walk rates higher than 10% in several seasons (though notably not since 2020). That wildness has caused more erratic game-by-game variation than expected for a starter of his caliber. Senga’s pitch movement can be very difficult for batters to pick up, but he doesn’t typically rely on hitting the strike zone very often, and he generally has zone rates lower than league average according to DeltaGraphs. He has only posted a first-pitch strike rate better than 50% once in his career. Senga’s velocity tends to get lower-end NPB players to cheat on the threat of the fastball, something which MLB batters will do less often. Overall, Senga’s command will need to take a step forward if he wants to reach his number two starter upside in MLB.

Perhaps more concerning is Senga’s extensive injury history. While he hasn’t had a severe arm injury since he missed a year with shoulder problems early in his career, every season has been riddled with minor issues that knock him out for a few starts at a time. This season he missed several starts with elbow soreness and about a month with COVID. The year before, he twisted his ankle fielding a ball and missed three months. That list goes on and on, and once you go back more than a couple years it also extends to scarier places like his occasionally-troublesome right shoulder. Senga has a high-effort short-armed delivery and a relatively slight frame for a starter at 6-foot, 178 pounds, and that long injury history raises concerns about how he’d transition from starting once per week to once every five to six days. Senga has only exceeded 150 innings in a season twice, and only once since 2017. There are multiple ways to view that: either he can’t stay healthy as a starter or his arm is more fresh than usual for his age. Time will tell how MLB teams view that potential red flag.

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Due to the injury history and command concerns, as well as seeing how dominant Senga has been in relief on international teams, as of a few years ago some scouts viewed him more as a reliever than as a starter. He will get paid starter money (and despite the injury history, it would not be surprising to see him get a four-year deal given how many teams are expected to be interested), but the bullpen could be a safe landing spot for him if things don’t go well. With the upside in his arm, and given that set-up pitchers are signing 4+ year deals already this offseason, that may make the risk of signing Senga a lot more palatable.

Ultimately, a pitcher with these tools — and with their overall value slightly suppressed due to injury risk — is very much the type of pitcher the Dodgers have liked to gamble on over the past few seasons, and they’ve been scouting him for over a decade. According to an early report by Jon Morosi, they are indeed interested, along with many other teams. While the risk is longer-term than the recent signings of Tyler Anderson and Andrew Heaney, it’s pretty hard to deny Senga’s sky-high talent. The fit is absolutely there, so we’ll have to wait and see if the injury history and high expected price tag scare them towards lower-priced or safer arms.

About Daniel Brim

Daniel Brim grew up in the Los Angeles area but doesn't live there anymore. He still watches the Dodgers and writes about them sometimes.