Who is Roki Sasaki and What Will His Challenges Be in MLB?

The word “phenom” has been thrown out plenty with 23-year-old right-hander Roki Sasaki, and understandably so. After breaking Shohei Ohtani’s Japanese high school fastball velocity record by touching 101 MPH with his heater, he earned the nickname “the Monster of the Reiwa Era” and began to take the baseball world by storm.

You know a player is a special talent when there’s more suspense around the draft lottery than the actual first pick on draft day, which was exactly the case when the Chibe Lotte Marines won the first selection and surprised nobody by later taking Sasaki in 2019.

Making his pro debut in 2021, Sasaki pitched to a 1.84 ERA at 19 years old, and the ball started rolling on his NPB dominance. He threw the league’s 16th perfect game in 2022 and tied Koji Noda’s single game strikeout record of 19 while standing alone as the only pitcher to strikeout 13 batters in a row.

He once again joined Ohtani in the velocity record books when he touched 102.5 MPH with his fastball on several occasions in 2023. Now Sasaki is taking another page out of Ohtani’s playbook, as he will be coming stateside before the age of 25.

Similar to when all NPB teams had that suspense leading into his draft lottery, Sasaki’s decision to come over now adds that same layer of intrigue towards his free agency, as technically any team can win the lottery of signing him from a financial perspective.

Unlike Yoshinobu Yamamoto a year ago, Sasaki is technically a minor league free agent (even though his first pitch of 2025 will surely come on a major league mound). Yamamoto was posted at 25 years old, which made him an MLB free agent, open to bidding to all teams for however much they were willing to pay.

This led to a bidding war that resulted in Yamamoto signing the richest contract in MLB history for a pitcher, a $325 million deal with the Los Angeles Dodgers. As a minor league free agent, teams are limited to spending only their international bonus pool to land his services.

This means that any team can sign Sasaki if they make a good enough pitch that they are the team to be trusted for the first six years of his MLB career. While we know Sasaki is a sensation, what are teams really getting when it comes to his pitch mix and how will it translate to MLB competition?

Although Sasaki is sure to be one of the top pitching prospects in baseball upon signing, there are still things the young phenom has to work through if he is going to ascend to the top of Major League Baseball. Here’s what we can learn from each pitch in his arsenal, as we project what Sasaki will be for his new club in 2025.

Roki Sasaki Scouting Report: What Pitches Does He Throw?

Roki Sasaki is most known for his devasting mix of a high-velocity fastball, which he pairs with a nasty splitter. This one-two punch of plus pitches has the chance to be as good as any mix in Major League Baseball. The key to unlocking Sasaki’s pitch repertoire to the highest level in MLB could be the continued development of a breaking ball, as a third pitch to keep hitters off-balance.

Sasaki’s Fastball

Roki Sasaki pitches off a fastball that was averaging around 99 MPH in recent years, but he saw his velocity dip by two ticks in 2024 as he dealt with what was later reported as “shoulder fatigue.”

Even with the drop in velocity, Sasaki’s heater is still comfortably above the MLB average of 94 mph. But, compounding with the dip in velocity was a loss of about two inches of induced vertical break, causing it to miss fewer bats within the strike zone. 

Even with the ride on his heater compromised some, Sasaki gets a good amount of run on the pitch as well, helping him pick up ground balls at an above average clip.

It’s nice to have that in his back pocket, but for him to be the overpowering strikeout artist he has been for the majority of his NPB career, it will be important for Sasaki to regain his velocity and life on his fastball as his movement profile from a slightly above average release height seemed to be much easier for hitters to get to in 2024.

It’s also worth noting that pitchers will generally lose around two inches of induced vertical break on their fastball when switching from the NPB ball to the MLB ball. If Sasaki does not rectify his step backwards fastball wise, it could really be compounded with an MLB ball, as he would likely see his induced vertical break drop to around 14 inches from an above average release height. 

It could merely be a matter of getting healthy for Sasaki as he looked to be compensating at times for his shoulder fatigue, releasing from a higher arm angle and steeper vertical approach angle.

When healthy, Saski’s fastball averaged nearly 17 inches of vert in 2023 with an MLB ball at the World Baseball Classic. 

Assuming the velocity and characteristics can return to his prior form, Sasaki would likely benefit from working towards the top of the zone more, particularly at the upper-armside quadrant where his fastball really takes off naturally. 

NPB teams are generally less likely to encourage their pitchers to elevate their heaters consistently, with Shota Imanaga serving as a prime example. In his first MLB season, Imanaga’s fastball percentage in the top half of the zone jumped by more than 12% compared to his last NPB season. 

While Sasaki is not as much of a low release, high carry guy like Imanaga, his sheer velocity paired with ride and run would surely miss more bats in the top half of the zone.

Sasaki threw roughly 58% of his fastballs in the top half of the zone in 2024, nearly the same figure as Imanaga’s final season in NPB. 

When Sasaki’s pitches were sitting 99 MPH and getting 18 inches of IVB in 2023, his fastball dominated in the top half of the zone, picking up an in-zone whiff rate of 28%. Even with his subdued fastball in 2024, the vast majority of his heater whiffs came at the top of the zone. 

Sasaki could benefit from adding a true sinker in order to get early contact and keep his pitch count down. With the arm-side run he already generates, it shouldn’t be too difficult to lean into a heavier fastball that could also create a difficult tunnel with his elite splitter. That said, his fastball and splitter already work off of each other in a way that maybe no other two pitches do in MLB. 

Strikeout and Soft-Contact Inducing Splitter

There is not a pitch like Roki Sasaki’s splitter in Major League Baseball right now.

Somehow moving like a gyro slider that he consistently locates at the bottom of the zone with impressive depth. The vertical break and horizontal break, at or below zero inches, already places the pitch in its own category. But the horizontal separation that he creates from his running fastball makes the pitch combination particularly unique. 

Sasaki’s more than 13 inches of horizontal separation between his fastball and splitter would be the largest gap in the Major Leagues between any fastball and changeup (edging out Cardinals right-hander Sonny Gray), while the vertical separation would slot in at 10th most. 

Sasaki’s 21 inches of separation both horizontally and vertically would be the second-largest differential in MLB behind only Trevor Richards.

While Richards is not the Cy Young caliber arm you’d expect to sit atop that list, he survived seven MLB seasons with just a below-average fastball and changeup.

Imagine what Sasaki could do at his velocity with a similar amount of separation between his fastball and splitter but at about seven ticks harder.

He rarely misses up with the pitch and even less frequently loses depth, with less than 3% of his splitters in 2024 featuring more than five inches of induced vertical break.

Even in the rare occasion where Sasaki leaves it elevated, the way it works off of his fastball and outlier action at 87-90 MPH results in big whiff numbers within the zone and plenty of weak contact. 

Since the start of the 2023 season, Sasaki racked up a ground ball rate just shy of 70% on the pitch with a chase rate (41%) nearly as high as the contact rate allowed (46%). The consistency blended with the action of the pitch makes it a reliable weapon against hitters from both sides of the plate.

Over that same span, NPB lefties and righties alike hovered around a .100 batting average against it. 

The fact that Sasaki’s splitter does not discriminate against handedness helps take the pressure off of his slider, but his struggles to spin a breaking ball–especially in 2024–makes it seem likely that whatever team signs him may guide him to a different-looking breaking ball. 

The Interesting Case of Sasaski’s Breaking Ball

The average shape of Sasaki’s slider was mostly unchanged from 2023, just seeing a slight gain in horizontal movement, though he threw the pitch four ticks slower at 83.6 MPH last season.

While the drop in velocity resulted in a 5% dip in terms of in-zone whiff, he seemed to have a better feel for the pitch, landing it in the zone with more consistency. 

As a result, Sasaki was more confident in weaponizing the pitch when pitching from behind or in even counts, taking advantage of the fact that hitters were likely geared up or cheating for a heater while trying to eliminate the splitter by selling out for a fastball that he generally likes to work towards the middle third of the plate and the arm side half. 

That seemed to be the approach for hitters against Sasaki in 2024 as the swing rate against his fastball jumped a few ticks, despite a roughly 13% dip in swing rate against his splitter.

Looking at the pitch data, density maps, and video, the drop in swing rate appeared to be a result of a more stubborn approach from NPB hitters rather than a lack of quality or command of the pitch.

Previously more hesitant to go inside to left-handed hitters with what is comfortably his least effective offering, Sasaki perhaps started to realize that opposite-handed hitters were eliminating the inside part of the plate with him, meaning if he could land his slider for a strike on the inner half when they’re likely hunting heater, it could result in a called strike or weak contact.

After sparsely throwing his slider to left-handed hitters in 2023, he gained enough confidence in it to use it in early counts against opposite-handed hitters. After starting just 10% of left-handed hitters with a slider in 2023, Sasaki more than tripled that figure in 2024 to 33%, with even-count usage seeing gains as well. 

Using the slider in early counts not only helped hedge a fastball that was less effective than Sasaki was used to, but it also allowed him to save his splitter for deeper counts and two strikes, a helpful wrinkle when the majority of your strikeouts against lefties come from that pitch alone. 

In a vacuum, the pitch could benefit from some tweaks, especially as Sasaki gets adjusted to an MLB ball, but it doesn’t necessarily need to be upgraded into a big whiff offering.

Sasaki’s ability to locate a pitch at a distinct third speed in counts where hitters may be geared for velocity or weary of a splitter resulted in a 15% increase in ground balls and pop-ups in tandem with the 5% increase in usage. 

Sasaki will likely need to tweak his breaking ball to yield similar results at the big league level, but his 2024 season provided valuable intel as to how helpful a breaking ball that he can land consistently for a strike can be for him, even if it is not a plus pitch. 

The slider he threw ranged widely in shape, sometimes moving like a slider with a bit of ride, while other times sporting more of a slurvier shape.

Sasaki landed his slider for a strike more consistently when it did not feature as much of the vertical drop or slurvy action. On sliders that featured zero inches of vertical break and above, Sasaki posted a 65% strike rate, about five percent higher than pitches south of the X-axis. 

What Should the Arsenal Look Like?

It’s clear that the first and foremost priority for Sasaki should be to get his fastball back to where it was in 2023. With that pitch and his splitter alone, his MLB floor is extremely high.

Given the fact that Sasaki is more of a pronator than a supinator, it will be important to see how his breaking ball moves with an MLB ball before whatever team that signs him will try to curate the optimal third pitch for him. 

He appeared to benefit command-wise from cutting down his breaking ball velocity some as well as working more horizontally. The velocity separation seemed to benefit Sasaki’s ability to keep hitters off-balance as well.

It’s a bit of a puzzle because Sasaki seems to command his more horizontal sliders better, but generally speaking, breaking balls with vertical depth will play better against opposite-handed hitters. It may be helpful for Sasaki to find two distinct breaking balls, even if one is far more effective than the other. 

A harder, shorter, cutterish slider could be an extremely effective weapon against lefties to supplement the fastball and splitter combination, and could be a solid offering to mix in against righties as well. A slower, bigger curveball can help provide those early “show me” strikes to lefties that he seemed to benefit from in 2024. 

If the aforementioned sinker is not in the cards for Sasaki, a cutter or that cutterish slider hybrid I just mentioned could serve as the weak contact-inducer and pitch count-saver.

Given the quality of Sasaki’s splitter and the sheer velocity of his fastball, the presence of a breaking ball that hitters have to at least respect will be essential in limiting their ability to shrink the zone.

A willingness to elevate his fastball more would help with that as well. 

Will He Make an Impact Right Away?

Clearly the stuff is ready to get big league hitters out, but there are some relevant hurdles for Sasaki in his adjustment to reaching his full MLB potential.

The most well-documented is his health and workload, and while it is important that he can build up to pitching more than his career-high 129 ⅓ innings in 2022, it’s not necessarily a barrier to big league success and a big payday… just ask Tyler Glasnow. 

That said, with the injury concerns he has faced over the last two seasons, a team that signs him may want to slow-roll him into his MLB starting role in order to more safely build him up and keep him available for the end of the season.

Seeing him handled similarly to how the Pirates managed Paul Skenes wouldn’t be entirely surprising. 

Where Sasaki will need to change his ways a bit is his tempo and ability to hold runners on. He exclusively works out of the stretch, with a big and slow leg kick with nobody on that morphs into a shorter slide step when runners are aboard.

The problem is, even the slide step is slow, mixing in far too many 1.6s to home, which has resulted in base stealers going 25-for-28 on Sasaki since the start of the 2023 season. 

In addition to being slow to the plate, Sasaki generally likes to take his time between pitches.

This is not uncommon at all for Japanese pitchers, as pitch clocks and pace of play are not an area of concern in NPB. In his first year stateside, Yuki Matsui was the slowest pitcher tempo-wise in MLB last season, and even Yu Darvish still hovers around the 19-second range between pitches a dozen years into his MLB career. 

Sasaki was capable of working more quickly in the WBC where he had to adhere to the pitch clock, but there may be an adjustment period for him to become fully acclimated to MLB’s pace of play. When things go south, Sasaki tends to slow down in the video I watched. 

He wears his frustration on the mound a bit more demonstratively than what folks are typically used to seeing in NPB, and with the presence of the pitch clock and stolen bases much more apparent in MLB, it wouldn’t be shocking to see Sasaki struggle with some snowball innings in the early going. 

Ultimately, Sasaki is a rare talent that would be commanding hundreds of millions of dollars in free agency if not for a complicated posting situation that only allows teams to sign him with money allocated from their 2025 IFA pool. 

With all 30 teams being able to offer Sasaki a relatively similar signing bonus, it will really come down to what he and his agent deem to be the best situation for him.

With still more development to be had, it makes sense that a team that excels in R&D like the Dodgers would be the favorites, even if they didn’t land two of the best Japanese players of all-time in recent years in Shohei Ohtani and Yoshinobu Yamamoto. 

Another favorite who seems to check several of Sasaki’s reported boxes is the Padres, who may not have as strong of a track record with player development but could make a strong pitch with their new biomechanics pitching lab that was unveiled earlier this year (with both Yu Darvish and Yuki Matsui at the ribbon-cutting ceremony.) 

Whichever team signs Sasaki will instantly inherit what is arguably the most unique two-pitch combination in Major League Baseball. From there, it will be fun to monitor how high the two parties can push the 23-year-old’s already lofty ceiling.