Sasaki's nasty stuff could make him MLB's next young ace

The Monster of the Reiwa is coming to Major League Baseball. So let's take a look at Roki Sasaki's monstrous stuff.

The 23-year-old fireballer has dominated in Japan, and he has the electric arsenal to do the same in MLB. We know he does.

We saw it on the international stage at the 2023 World Baseball Classic -- where there was Statcast tracking for both of Sasaki's starts, against the Czech Republic and Mexico. That means we have data on Sasaki already. And the early numbers show you why he's going to be one of the most coveted Japanese superstars ever to jump to the Major Leagues.

Here's a preview of the type of stuff we're hoping to see from Sasaki in MLB, based on what we saw from him at the World Baseball Classic.

1) He should have one of the highest-octane fastballs in the Majors

Sasaki's four-seamer in the WBC averaged 100.3 mph.

He topped out at 101.9 mph, hitting that mark three times.

Forty-seven of his 65 tracked fastballs -- 72%, nearly three-quarters -- reached triple digits. A dozen of those were at least 101 mph.

Let's take a look at the Major Leagues in 2024. The only starting pitcher to hit 100 mph that many times in the full season was Paul Skenes … the phenom whose status Sasaki will rival as one of the most-hyped MLB pitching prospects ever. Skenes threw exactly 100 pitches 100 mph or faster in his rookie season.

Sasaki's best heater of the tournament was a 101.8 mph fastball to blow away Randy Arozarena. Sasaki threw it right down Broadway; Arozarena still couldn't catch up.

Sasaki also got whiffs on four-seamers clocked at 101.3 mph (a strikeout of the Czech Republic's William Escala), 101.3 mph again, 100.7 mph, 100.2 mph and 100.1 mph. He generated a 35% whiff rate overall.

He also showed good ride on his four-seamer in the WBC, averaging 17 inches of induced vertical break -- which would make it an above-average "rising" fastball that would likely get swings-and-misses -- as well as 12 inches of arm-side run.

Because Sasaki's start against Mexico in the WBC semifinals was at the Marlins' loanDepot park, it was tracked by Hawk-Eye high-speed cameras. So we can see just how a Sasaki fastball explodes toward the hitter via 3D tracking.

If Sasaki brings anything close to his WBC fastball to the big leagues, it'll be a big-time heater, similar to the ones some of MLB's top power pitchers throw.

The questions are what that velo and rise will look like over a full Major League season instead of a short tournament where pitchers let it rip with everything they have -- especially after Sasaki's velo dipped in the 2024 NPB season.

He averaged close to 99 mph over the 2023 season after returning from the World Baseball Classic, but this year, Sasaki's four-seamer averaged just under 97 mph, according to available NPB data. That may have been due to him dealing with injuries during the season -- an oblique injury as well as arm issues that have been reported as arm soreness or shoulder fatigue. If Sasaki arrives in the Majors at full health, and his fastball velo is back up to where we've seen it, look out.

2) His splitter might be the best in the world

Triple-digit fastballs turn heads, but the gem of Sasaki's arsenal is his splitter. It might be the best splitter in the world already, and it could be the best splitter in the Majors in 2025.

Sasaki's splitter in the WBC averaged 90.9 mph. He threw it as hard as 93 mph -- and that one got a swing-and-miss from Alex Verdugo.

Only three Major League starters averaged a 90-plus mph splitter in 2024: the Angels' José Soriano (92.6 mph), the Rays' Taj Bradley and the Dodgers' Yoshinobu Yamamoto (90.2 mph), in whose footsteps Sasaki will be following. You can count Skenes' 94 mph splinker, too, if you want -- it gets classified as a sinker but it's a hybrid pitch with splitter movement.

At that high velocity, Sasaki's splitter movement is just filthy. It drops a ton, averaging 33 inches of downward vertical movement in the WBC. As for the horizontal break? That's kind of unique. Sometimes Sasaki's splitter fades … sometimes it cuts. It can break in either direction, and that makes it even more unfair.

The World Baseball Classic hitters' swings against the Sasaki split-finger showed just how unfair. He induced a 60% whiff rate with his splitter in the tournament, getting 18 whiffs on 30 swings. He got eight strikeouts on the pitch -- all swinging.

That absurd swing-and-miss rate has stayed true in NPB, even with Sasaki's splitter velocity dropping a little bit, like his fastball, from right around 90 mph in 2023 after the WBC to just above 88 mph in 2024. His splitter whiff rate was 52% in 2023 … and 57% in 2024.

Those whiffs should translate straight to MLB -- after all, he was making plenty of MLB hitters look silly in the WBC. Here's what some of those splitters look like with 3D tracking.

Like Skenes with his "splinker," Sasaki has a wipeout offspeed pitch that steals the show from his 100 mph heaters. Of all the great Japanese aces who've brought elite splitters to MLB -- Shohei Ohtani, Yamamoto, Shota Imanaga, Kodai Senga -- Sasaki's just might be the best one.

3) His slider has nasty potential

Sasaki barely even needed his slider in the World Baseball Classic, thanks to his ridiculous fastball-splitter combo.

But he does throw a slider, and it does have the makings of a plus No. 3 pitch that he can use in the big leagues -- especially if he can throw the hard, bullet slider that a lot of MLB aces do.

Sasaki's slider in the WBC looked close to that kind of hard slider/cutter hybrid style of pitch, as he averaged 88 mph with about six inches of horizontal break, getting pretty tight movement.

He got some nice swings-and-misses on it, too, including one against Arozarena at 88.2 mph and a nasty strikeout of the Czech Republic's Martin Muzik at 89.1 mph.

Here's what a Sasaki slider looks like in 3D.

Sasaki will need to get that "hard slider" velocity back when he comes to MLB. His velo on that pitch dropped a lot in NPB this year, from close to 88 mph in 2023 following the WBC all the way down to under 84 mph in 2024. As pitching analyst Lance Brozdowski notes in his great breakdown of Sasaki's repertoire, he doesn't seem to have enough spin on his slider to be able to turn it into the slower, more horizontal "sweeper" variety as a Major Leaguer.

But if Sasaki is throwing his World Baseball Classic slider in the big leagues, that's a different story. If he has the fastball, splitter and slider all working, like he showcased in 2023, then MLB will have its next great young ace.