This advanced metric might've finally told Dodgers fans what's wrong with Roki Sasaki

When the Los Angeles Dodgers signed Roki Sasaki last winter, it felt less like a free-agent acquisition and more like the arrival of a phenomenon. He was viewed as a generational arm with triple-digit velocity, a devastating splitter and international hype rarely seen for a pitcher still in his early 20s.

And yet, one year later, an uncomfortable question is beginning to surface: what if the warning signs were always there?

According to the 2026 Worst Pitcher proStuff+ leaderboard from Pitch Profiler, Sasaki owns a 93 proStuff+, the sixth-worst mark in baseball. That number doesn’t measure results. It doesn’t care about ERA or postseason heroics. It strips pitching down to the raw ingredients — velocity, movement profile, spin efficiency and release characteristics — essentially asking one question: how good is the actual “stuff”?

For Dodgers fans trying to understand Sasaki’s uneven rookie season and shaky spring debut, the answer may be unsettling. Because the model suggests the underlying arsenal simply hasn’t been as dominant as advertised.

On paper, nothing looks wrong. Sasaki’s fastball still touches 98 mph. The arm speed remains explosive, and the splitter flashes brilliance. But velocity alone doesn’t create elite pitches anymore. Shape, vertical break, and release consistency all matter.

Sasaki’s profile suggests his pitches may be easier to track and square up than expected — which explains why 2025 often felt like a grind. He posted a 4.72 ERA. Pitch counts ballooned early in games. Command frequently deserted him. Eventually, a shoulder impingement shut him down for months and raised legitimate fears about whether he would pitch again that season.

When Sasaki returned late in September — shifting into a closer role out of necessity — he became a postseason hero. The Dodgers almost certainly don’t win a second straight World Series without him. But October adrenaline can hide flaws that a six-month rotation workload exposes.

Roki Sasaki's proStuff+ ranking may explain his struggles with the Dodgers

Sasaki's first outing this spring felt familiar. He threw 36 pitches — only half of which landed in the strike zone — over 1 1/3 innings, giving up three runs and two walks. It looked eerily similar to last season’s struggles: electric flashes interrupted by inefficient innings. That’s where proStuff+ becomes revealing.

If the physical pitch characteristics themselves grade below average, command issues become magnified. There’s less margin for error, and miss locations get punished more quickly. Suddenly, the inconsistency makes sense.

Manager Dave Roberts has been candid this spring in saying Sasaki needs a third pitch. The Dodgers are experimenting with both a two-seamer and a cutter — attempts to create different movement planes and keep hitters from sitting on the fastball-splitter combination.

Modern lineups adjust quickly. Facing hitters three times through the order demands unpredictability, not just velocity. If proStuff+ is correct, diversification isn’t a luxury for Sasaki. It’s the only path toward becoming the ace many expected him to be.

Fortunately, there’s reason for optimism. Sasaki is fully recovered from last year's shoulder injury, and stuff metrics can change faster than reputation. Pitch design labs — something the Dodgers arguably do better than anyone in baseball — specialize in reshaping arsenals. Adjust a seam orientation, change a release window, add a few inches of horizontal movement — and suddenly, a 93 becomes a 105.

The Dodgers have turned pitchers into stars before. They clearly believe Sasaki can be next.