What do you think you know about sliders?
Let Tatsuya Imai throw that out the window.
The Astros' new starter broke the Baseball Internet this weekend with his "wrong-way slider," and -- well, you'll just have to watch it.
That's … not the way a slider is supposed to move.
A slider is supposed to break to the pitcher's glove side. Everybody knows that. For any normal right-handed pitcher, a slider moves from right to left, away from a right-handed batter and in toward a lefty.
So why is Imai's skidding off in the opposite direction?
It's not an optical illusion, either, the way a "rising" fastball is. Imai's slider really does run from left to right. Through his first two Major League starts, he's averaging six inches of "wrong-way" movement on his slider.
The average slider thrown by an MLB right-hander breaks four inches to the glove side. Imai's slider runs six inches to the arm side. That's a 10-inch gap in horizontal movement between Imai's slider and the average slider, putting his slider squarely on the side of the pitch movement chart where you'd expect an offspeed pitch like a splitter or changeup, not a breaking ball like a slider or curve.
Now, we actually already knew that Imai's slider moved backwards like this, even before he made his Astros debut. It was in all the scouting reports when he came over from Japan's Saitama Seibu Lions this winter. It was one of the most interesting qualities Imai was supposed to have as a pitcher.
But to know about the pitch is one thing. To see Imai's wrong-way slider in action in real big league games is a whole different story.
This thing is nasty. And Imai's start against the A's this weekend -- a nine-strikeout scoreless gem -- was the first time he really put the slider on full display in an Astros uniform.
"It was kind of doing everything," said the A's Jeff McNeil, who struck out against an 87 mph Imai slider that broke five inches to the arm side. "Some went left. Some went right. It was pretty interesting to see. You don't see a lot of pitches like that."
Imai can generate an absurd amount of wrong-way movement when he snaps off his best sliders. The slider that Imai threw to Tyler Soderstrom -- the one in that first Pitching Ninja clip up there -- that one broke 13 inches to Imai's arm side.
How is a hitter supposed to deal with that when he never sees other sliders that look similar?
Imai's slider doesn't just look unique to the naked eye. It is unique.
The Statcast data for Imai's slider is unlike pretty much every other slider in Major League Baseball.
So far this season, 201 pitchers have thrown at least 10 sliders. Ninety-six percent of those pitchers get normal glove-side movement on their sliders. Only nine out of 201 average any amount of arm-side movement. But Imai stands alone even among that tiny group. He's averaging three times as much arm-side slider movement as anyone else.
Pitchers with "wrong-way" slider movement, 2026
- Tatsuya Imai (Astros): 6 inches
- Alex Lange (Royals): 2 inches
- Wandy Peralta (Padres): 1 inch
- Lucas Erceg (Royals): 1 inch
- Brock Burke (Reds): 1 inch
- George Klassen (Angels): 1 inch
- Connelly Early (Red Sox): 1 inch
- Cole Wilcox (Mariners): 1 inch
- Joe Ryan (Twins): <1 inch
Even if you compare Imai this season to all Major League pitchers last season -- an even larger sample of over 700 slider throwers -- Imai is topping the list by doubling up everybody else.
The next-closest pitcher you see is Blue Jays star rookie Trey Yesavage, followed by the Reds' Chase Petty and the Pirates' Dauri Moreta, who all averaged about three inches of arm-side slider movement in 2025.
Even if you compare Imai to Yesavage -- whose wrong-way slider also made waves when he emerged as a postseason phenom -- Imai's wrong-way slider is a lot different from Yesavage's wrong-way slider.
Yesavage's slider moves to the arm side because he throws from such an extreme over-the-top arm angle. His unique delivery lets his slider roll toward the arm side instead of snap to the glove side.
But Imai throws from a much lower sidearm angle. His arm angle is more than twice as sidearm as Yesavage's, in fact, and he releases his slider from nearly two feet closer to the ground.
A sidearm delivery like his would normally produce easy glove-side break on a slider. So how does he get movement to the opposite side instead?
The key is how he releases his slider. Imai's pitching hand gets under the baseball when he lets his slider go, which is what generates the arm-side run.
That is a slider release you just don't see every day.
Imai's slider moves almost like a screwball. Besides the handful of other wrong-way sliders like Yesavage's, Brent Honeywell's screwball is one of the closest things to Imai's slider in terms of movement.
But it's not a screwball. It's a slider, and a good one. Imai doesn't throw it like a screwball at all, which would involve turning his hand over the top of the baseball, not scooping underneath it.
Seeing Imai's slider release up close this weekend naturally produced a fun frenzy as people in the pitching world tried to figure out how in the world he does it.
Driveline's Sam Ehrlich and Jack Lambert attempted to recreate Imai's slider in the company's pitching lab -- with Ehrlich first using computer vision to reverse-engineer the seam orientation and spin direction of Imai's slider, and then Lambert making himself the guinea pig as he tried to actually throw the pitch.
That's what happens with pitch design these days. We see someone throwing a uniquely nasty pitch, and suddenly everyone's trying to solve the puzzle of how it's done.
Imai's wrong-way slider is the type of pitch that can inspire us like that.