How Trevor Bauer Remade His Slider — And Changed Baseball

Travis Sawchik is a FiveThirtyEight staff writer. His new book “The MVP Machine: How Baseball’s New Nonconformists Are Using Data to Build Better Players,” co-authored with The Ringer’s Ben Lindbergh, is available this week. In it, they examine how outsiders (and a few forward-thinking insiders) are employing unconventional ideas along with new data from new technology to lead a bottom-up revolution in improving skill levels. We’re publishing an excerpt of the book on how Cleveland Indians pitcher Trevor Bauer, a trailblazer in player development, used new technology like the high-speed Edgertronic camera, which he introduced to baseball — along with some stealthy reconnaissance — to fuel his 2018 breakout. It was Bauer who ushered a new, game-altering field into the sport: pitch design.


As April went on, Bauer became increasingly frustrated with his slider. Each time he sat in front of his locker after games and pulled up the pitch’s horizontal movement on his smartphone, he noticed it declining. His off-season project was failing. Although he’d had a fine first month (2.45 ERA, 46 strikeouts and 16 walks in 40 1/3 innings), he was frustrated with the pitch’s lack of improvement and doubted he could sustain success without it.

On April 1, his slider averaged 6.7 inches of horizontal movement. In his second start on April 7 versus the Royals, the horizontal movement fell to 6.2 inches, and then to 4.5 inches on April 12 at Detroit. He wanted 10 inches of horizontal movement. Although he was pitching relatively well, he was also facing some of the weakest teams in baseball. In terms of performance against extra-divisional opponents, the 2018 AL Central was the second-weakest division of all time, and Bauer didn’t have to face its best team. On April 20 at Baltimore, the horizontal movement averaged 5.1 inches. He also wanted the slider to have zero inches of vertical depth to keep it on the same plane as his fastball for as long as possible, creating deception. Instead it was breaking 3 to 4 inches. The slider was behaving like a less effective version of his curveball.

The Indians did not travel with their Edgertronic camera, Bauer says, and its use at home was sporadic. There were occasions when the camera wasn’t used because a Fox Sports TV camera occupied the camera well behind the plate. “The TV guys were down there,” Bauer recalls the club explaining. “I don’t give half a fuck,” he said. “Tell the TV guys to get out of there.”

The Indians’ video personnel also lacked familiarity with the device, and as a result, some bullpen sessions were not recorded properly. It was all maddening to Bauer. There was another potential use of the camera that the Indians weren’t fully exploiting, although the Astros—and Bauer before them—had done so previously: intelligence gathering. Bauer didn’t just want to study himself; he also wanted to study the other best pitchers in baseball. The ironic thing about criticism from past teammates like Miguel Montero was that Bauer didn’t believe he had all the answers. He was always searching for better information and practices.

On his own team, Corey Kluber and Clevinger had two of the best sliders in baseball. As Bauer designed his slider in the winter, he had studied their grips, which he had filmed the previous season. And on April 13, there was another pitcher he wanted to study: Toronto’s Marcus Stroman.

Stroman and Bauer had long admired each other from a distance. Prior to being selected in the first round of the 2012 draft, Stroman called Bauer a “pioneer to the pitching world” on Twitter. Stroman said he used to watch tape of Bauer’s UCLA starts in his Duke dorm room. Bauer cited Stroman as his favorite non-Cleveland player to watch. Now Bauer wanted his elite slider.

Leading up to that start on a frigid April evening, Bauer hounded the video staff and its coordinator, the white-haired and studious looking Bob Chester, to make sure they got Edgertronic footage of Stroman. But in the first inning, as Clevinger pitched for the Indians, neither Chester nor the camera was in the camera well behind home plate. If this start wasn’t filmed, Bauer would be livid. Between innings, Chester and the Edgertronic appeared in the camera well. As Stroman started pitching, Chester attached the camera to a tripod directly behind home plate. He then left the area. But the camera view was obstructed. This was Bauer’s one chance to get a look at Stroman and his slider on the Edgertronic. The first inning was over, and there was no usable footage. But Chester, realizing the error, returned in the second inning and repositioned the camera more to the left of the plate, allowing for an unobstructed view of Stroman. It was perhaps the most important repositioning of a high-speed camera in the brief history of pitch design.

After the game, Bauer immediately dove into the video: eleven minutes and fifty-one seconds’ worth of Stroman throwing pitches, a global shutter capturing every detail in thousands of frames per second. In May, he shared the video with Travis and motioned to Stroman’s right hand. “You see his thumb?” Bauer said. “It slips really early.”

That was the key. As Stroman’s upper body rotated and his right hand came through to throw, his thumb lost contact with the ball first, with his index and middle fingers still in contact before release. The middle finger was on the far side of the ball, the index finger behind the ball. Bauer paused the video.

“His middle finger never gets to the front of the ball. It just kind of brushes the side of it,” Bauer said. “Then you can only see his pointer finger appear once there is separation between the ball and his hand. … The pointer finger pushes the ball [to Stroman’s left], which puts more of a sidespin component on the ball. When I saw this video I was like, I have to find a way to get my thumb to slip earlier while my hand is still behind the ball.”

Two days later, Bauer threw his bullpen indoors, in a concrete bunker in the depths of Progressive Field. He commandeered the Edgertronic and filmed the session. One of his first throws resulted in a nearly perfect gyroball; not what he wanted. His index and middle fingers wrapped too much around the ball. His thumb was still in the way. To get his thumb to leave the ball earlier, he tried tucking it under the ball. This would push the axis up, he hoped, creating more sidespin and resulting in more lateral movement. One of his first attempts resulted in a pitch that got away from him; had a right-handed batter been in the box, it would have hit him in the helmet. He adjusted, applying more pressure with his index and middle fingers on the far side of the ball, running along the wide part of the figure-eight seam. Progress. The axis tilted up slightly, but not enough.

Bauer took his experiment to the mound over the following four starts at Baltimore on April 20 (5.1 inches of horizontal movement), against the Cubs at Wrigley Field on April 25 (4.8), at home against the Rangers (5.4), and at Yankee Stadium (4.4). It still wasn’t working. A day before his May 11 start at home against Kansas City, Bauer discovered something while lobbing balls back toward the infield during batting practice. Instead of gripping the “horseshoe” part of the seam with his middle finger as he had since the winter—and as most pitchers do when throwing a slider—he tried throwing one with a two-seam fastball grip, only tucking his thumb like Stroman. He spread his index and middle fingers over a narrower stretch of parallel seams and tucked his thumb and locked his wrist as he always did.

“I was like, holy shit,” Bauer recalls. “I could definitely see that the axis was different. I’m throwing the ball toward the collection bucket. I just flipped a couple. I saw a left-handed turn. … I said, I’m going to try that tomorrow.”

The grip allowed his thumb to get out of the way, to create a pitch with a more vertical axis. His index finger made the last contact with the ball, just brushing it, to create an element of sidespin. He had the gyro spin and sidespin mix he was seeking. He knew he couldn’t get a perfect north–south axis. He was hoping to create an axis pointed toward him at about 60 degrees. Most pitchers don’t experiment in games. They save experimentation for bullpens. But Bauer doesn’t mind failing before thousands. That’s one benefit of having a low threshold. You don’t care what anyone thinks if you are doing what you believe is right. If Bauer listened to his pitching coach and was always agreeable, he argues, he would not have a career. “And people wonder why I have the reputation of not listening to coaches,” he says.

On May 11, Bauer used the new grip for two innings, the second and third. His slider began to dart horizontally. As he examined the data after the game, he saw that one slider had moved eight inches. He was thrilled, at least until he learned that only one inning had been captured on the Edgertronic. While the pitch moved like he desired, he couldn’t control it.

“I switched back [during the game] because I had no idea where it was going,” he says. “I was in self-preservation mode. I switched back to my old grip, which was more comfortable, but it didn’t have the profile.”

The start was a disaster: he allowed five runs and eleven hits in 4 2/3 innings. But it may have been his most important start of the season. The grip had given him the movement he wanted. The Indians next traveled to Detroit, where Bauer threw his bullpen. He felt he was able to replicate the grip and axis. Those watching the bullpen session had their doubts that it was an improvement. “In my head I was throwing a freaking party,” Bauer says. “I went with it exclusively, and the movement profile was drastically different.”

With greater confidence in his new slider grip, Bauer took the mound on an afternoon getaway day at Comerica Park in Detroit. The stands at the home of the rebuilding Tigers were mostly empty. With two outs in the first inning, Bauer faced a 2–2 count against Nick Castellanos. Bauer threw a slider with the new grip. Behind the plate, catcher Roberto Perez held his glove outside and just below the strike zone. The pitch appeared to make a left-handed turn as it neared the plate, darting into Perez’s glove. Castellanos swung and missed. In the second inning, Bauer threw another two-strike slider to the Tigers’ John Hicks, a league-average hitter. Again, the slider appeared to be headed for the center of the plate before breaking to the left. Hicks also swung and missed.

One reason Bauer had longed for a slider was to pair it with his two-seam fastball, the laminar express. Because they both have little vertical movement, the two pitches could share the same path, or tunnel, for much of their journeys toward the plate but break horizontally in opposite directions too late for batters to adjust. To start the fourth inning, Bauer threw a 95 mph, two-strike two-seamer to the right-handed- hitting Pete Kozma. The pitch’s axis allowed for a smooth spot to develop near the nose of the ball. As it neared the plate, the turbulent air on its backside compelled it to break back toward the plate and catch the outside part of the strike zone. Kozma gave up on the pitch, thinking it was outside. Instead, he stared at strike three.

With two outs in the seventh, Bauer again faced Hicks. On a 2–2 count, Bauer threw an excellent slider. It held its plane, masquerading as a fastball bound for the outside corner before darting away. Hicks whiffed to end the inning. Bauer looked businesslike as he walked off the mound, as if he had done this before. But he hadn’t, and inside his head he was celebrating. It was arguably the finest start of Bauer’s career: eight innings, four hits allowed, no runs, no walks, and ten strikeouts. All ten of the Ks had come via whiffs on sliders or batters looking at his comeback two-seamer. That day, Bauer threw his new slider sixteen times and induced eight swings-and-misses: an outstanding 50 percent whiff rate, the best of all his pitches in the outing.

The pitch had an average horizontal movement of 8.6 inches, nearly what he wanted and roughly double where it had been in the previous six starts. The slider also averaged 0.3 inches of vertical movement relative to gravity. It was nearly perfect.

Through his first nine starts, Bauer owned a 2.59 ERA and a 2.82 FIP. He had struck out sixty-seven batters in fifty-nine innings and allowed just forty-five hits and only in his last outing had his pitches felt fully operational. He was as close as he’d ever been to becoming what he thought he could be.


Excerpted from “The MVP Machine: How Baseball’s New Nonconformists Are Using Data to Build Better Players” by Ben Lindbergh and Travis Sawchik. Copyright © 2019. Available from Basic Books, an imprint of Hachette Book Group, Inc.