**************************************** Regarding Yoshinobu Yamamoto, I happened to write an article around this time last year like the one below. Apparently, this piece has been linked somewhere, as it still regularly appears in my blog’s “Most Read Articles” list. My Impressions While Watching Yoshinobu Yamamoto Pitch (Memo)
Some of my observations at the time were on target, others completely missed the mark. Still, I’m genuinely happy to see that Yamamoto has overcome the issues he faced back then and is now recognized as one of the very best pitchers in the majors. I believe this is not simply a matter of him adjusting to the MLB environment—it must also be the result of tremendous effort and study on his part.
By contrast, the situation facing Roki Sasaki right now is even more concerning than Yamamoto’s was last year. His fastball—supposed to be his lifeline—isn’t firing. The radar gun reads mostly between 150–155 km/h (93–96 mph), and the spin rate is reportedly among the very worst for MLB starters. Batters seem to pick up the ball well, and he’s having a hard time generating swings and misses. On top of that, his forkball control is shaky, so hitters can sit on the fastball.
Sasaki is remembered for his spectacular run in NPB, with two consecutive perfect games (one incomplete) and a fastball that regularly hit 160 km/h (99 mph). He even outdueled Yamamoto in an ace-versus-ace showdown. I never expected him to instantly dominate MLB as he did in Japan, but I didn’t foresee this level of struggle either. (I had imagined a pattern where he would leave a strong impression in a few games, suffer an injury, then return—repeating that cycle.)
Common opinions online include:
He hasn’t yet adjusted to MLB’s slicker baseballs and harder mounds.
At 23, he’s still in a developmental stage—people should take the long view.
Without adding another pitch, success in MLB will be tough.
Learning the slider may have reduced his fastball velocity.
He could be protecting a shoulder or elbow issue, leading to mechanical breakdown.
He has never pitched a full season; without building up stamina, he won’t hold up.
As a power pitcher, he may already have peaked.
The complexity here is that two separate issues are intertwined: (1) he hasn’t fully adjusted to MLB conditions, and (2) his fastball velocity has dropped since last year and hasn’t recovered.
The most puzzling aspect isn’t just the loss of velocity—it’s the drastic decline in spin rate, to the point that some call his fastball among the worst in the league. In Japan, his fastball spin rate was measured at 2,450 rpm—above the NPB average of 2,200–2,300 rpm. Could MLB’s slicker baseballs really cause such a drop? (For example, Shota Imanaga still relies heavily on his high-spin fastball in MLB.)
Another mystery is the quality of his forkball. It’s now described as resembling a slow, low-spin knuckleball—something that could be called a “magic pitch” in itself. However, the large speed gap from his fastball makes it easier to read, so batters often disregard the forkball and sit on the heater. Back in Japan, he was known for a high-speed forkball near 150 km/h (93 mph), but it seems he can no longer throw it.
His 160 km/h+ fastball in Japan wasn’t a one-off—he regularly threw around that speed in 2023. At that time, his velocity and spin rate would have ranked among the best in MLB, which is why teams engaged in such an intense bidding war for him.
When his velocity dropped in 2024, cynical fans speculated that he might be “saving his arm” for MLB or pacing himself to avoid injury. However, reports say that when Sasaki’s camp evaluated MLB teams, they actually asked each club to present a “prescription” for restoring his fastball velocity. This suggests that even last year, it wasn’t about holding back—he was physically unable to reach his previous speeds. Combined with unfamiliar MLB balls and mounds, his command of both fastball and off-speed pitches has unraveled, leaving him in his current predicament.
Even former MLB stars are raising questions: Former MLB Star Questions Sasaki’s Velocity Drop: “Was the WBC Radar Gun Accurate?” “Maybe He’s Injured”
I didn’t follow Sasaki’s NPB career all that closely, so I can’t speak as an expert, but my amateur impression is that his delivery now looks stiff—almost like a machine running without lubrication—and his shoulder and arm range of motion seem reduced. When he pitched his perfect game, his motion was looser and more fluid, with greater whip.
Though he’s never been reported as having a major injury, he frequently rested during his time with the Chiba Lotte Marines. Some critics mocked him for “slacking off,” but I’ve long suspected he’s had chronic shoulder or elbow concerns. Even without clear imaging evidence, if he feels discomfort while pitching, it’s natural for him to subconsciously alter his mechanics, which could explain the drop in velocity.
In searching online, I found this passage from Sports Hochi, which I think is highly significant but hasn’t gotten much attention: Sasaki Reveals Rookie-Year Elbow Injury as Factor in Early MLB Move: “I Never Knew When I Might Not Be Able to Pitch”
In his rookie season of 2020, before Opening Day, he was injured during a simulated game. “I had a muscle strain in my right elbow and went through rehab, but the recovery was slow,” he said. He visited numerous hospitals, and at one point a doctor even recommended Tommy John surgery because he could no longer pitch pain-free with his original delivery.
The true cause was later discovered: poor shoulder condition had increased nerve tension, resulting in pain on the inside of his elbow, though the ligament itself was completely fine. Still, “I realized that just one pitch could end my career. With that uncertainty, I felt it was best to challenge MLB now rather than wait two years,” Sasaki explained, citing the injury as a factor in his decision to move.
The explanation is somewhat vague, but I suspect this shoulder/elbow issue has become chronic. MLB’s slicker ball requires a firmer grip, which could be putting even more strain on those areas. Over time, a protective delivery may have become ingrained, altering not just his velocity but also the quality of his fastball.
If the shoulder isn’t 100%, it’s hard to simply “pitch through it” to fix mechanics, and strength training also carries risk. It might not be a case of slacking off—rather, he may be physically unable to train aggressively.
This situation reminds me of former Yakult ace Tomohito Ito. His slider in his debut season was one of the best I’ve ever seen in decades of following pro baseball, easily top five. But shoulder problems cut short his prime. I would hate for Sasaki to become someone fans talk about in the past tense—“He was amazing back when he threw that perfect game,” “That was his peak.” I truly hope he can somehow regain the fastball he had two years ago, though I don’t know the exact path or prescription to make that happen.
Postscript: One week after I wrote this article, Sasaki was placed on the injured list with shoulder impingement syndrome. Even if the pain subsides, I think it will be difficult for him to succeed without making adjustments. I hope he takes his time this season—either restoring his old delivery or mastering a new pitch like a two-seamer—so he can come back strong next year.