In May Paul Skenes, a then 21-year-old pitcher, debuted on a Major League mound, 10 months after the Pittsburgh Pirates selected him as the first overall pick in the professional baseball draft. Before he threw a pitch in the big leagues, Skenes had been anointed as the sport’s next great hope on account of his electric fastball; he is one of a rising generation of pitchers who routinely throws above 100 miles per hour, a mark that was seen as an upper physiological limit as recently as a decade ago.

During his first two games, Skenes threw 29 pitches above 100 mph and exhibited the kind of screen-ready cockiness that recalled famed player Roger Clemens. When a reporter asked Skenes how he’d deal with hitters adjusting to his repertoire, he chuckled, “Go ahead and adjust. Good luck.” One writer called him “the perfect baseball prospect through every possible lens.” Rob Friedman, a popular social media personality and analyst who goes by the moniker Pitching Ninja, called him “the filthiest pitcher on freaking Earth.”

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But simmering beneath the rhapsodic excitement was a fear that others voiced: How long would it be before Skenes, like so many recent flamethrowers, injured his pitching arm?

Baseball has never been faster. The games fly by in two hours, and more pitchers are throwing harder than ever before. When Aroldis Chapman entered the league in 2010, he was seen as an anomaly for throwing above 100 mph. (He still holds the official record for the fastest pitch ever thrown, at 105.8 mph.) Since Chapman debuted, the average fastball speed has jumped by two miles per hour, and the number of pitches reaching the 100 mile per hour threshold has quadrupled. This growing emphasis on speed appears to be coming at a cost.

In recent years some of the game’s best and most exciting pitchers—including Spencer Strider, Gerrit Cole and Shohei Ohtani, the undisputed face of the game—have suffered injuries to their elbow. “Training has increased, and techniques have gotten better, so as a result, you have a lot more people throwing the ball harder,” says Koco Eaton, team surgeon for the Tampa Bay Rays. “There’s more stress to the system and more injuries.”

How did this happen? From 2012 to 2022, not counting 2020, Major League Baseball (MLB) suffered a 14-percent decline in game attendance. At the same time, the era of optimization was rising, and teams were using data analytics and technology such as video analysis to try to gain any advantage they could. “Analytics are very disruptive to any industry,” says Brian Bannister, current director of pitching for the Chicago White Sox, who was at the forefront of the trend while working with the Boston Red Sox and San Francisco Giants. “They distort the game and reprioritize things.”

In this case, analytics reprioritized velocity as well as what pitchers refer to as “stuff”: the mix of curving, sliding and sweeping pitches, most of them pivoting off a fastball, that can fool the best hitters on Earth. Companies such as Driveline and Tread Athletics—the latter co-founded by Ben Brewster, a former Minor League pitcher and author of Building the 95 MPH Body—began training both amateur and professional pitchers with the aim of getting the most out of each arm. At Tread’s 33,000-square-foot facility in North Carolina, every pitch is captured on screens and analyzed, so that coaches can refine players’ grip and figure out which pitches work best together.

In advance of the 2023 season, MLB instituted new rules to make games more viewer-friendly, with a pitch clock to keep games under three hours and larger bases to incentivize stealing. Viewership shot up, but so, too, it seemed, did injuries to the sport’s hardest throwers.

Last summer Ohtani, now star of the Los Angeles Dodgers, was found to have a tear in the ulnar collateral ligament (UCL) of his pitching arm, ending his season. (It was the second time he’s suffered the injury.) Shortly afterward, Gerrit Cole, last year’s American League Cy Young Award winner and one of the game’s hardest throwers, went down with inflammation in his elbow. Then the Cleveland Guardians announced that Shane Bieber, the team’s ace, would undergo UCL reconstruction, commonly known as Tommy John surgery. Around the same time, Spencer Strider, ace of the 2023 National League champion Atlanta Braves, tore his UCL.

It is accepted that the UCL can withstand 30 pounds of force; throwing a Major League fastball creates twice that much. The human body compensates for that pressure with the complex of muscles and tendons around the ligament. (Pitchers can now emerge from surgery with their UCL sheathed inside a device known as an internal brace—a suture system designed to protect the ligament.)

MLB has disputed that the pitch clock increases injuries. But there is concern among baseball’s top minds that the financial pressures to maximize velocity on every pitch, combined with the shortened recovery time between pitches, poses new risks. “What we’ve done, at all costs, is train pitchers and alter the usage of pitchers and encourage pitchers to go out there [and] throw as hard as possible, as often as possible,” says Bannister, who now counts himself as a skeptic of the leaguewide move toward absolute optimization.

Baseball is still called a national pastime, but the application of the moniker seems to be rooted in nostalgia. The heart of the game has long been in its quiet moments—the thick air of expectation that hovers before a fly ball drops into an outfielder’s glove while a runner prepares to try to tag up or the way a pitcher looks at a hitter when the tying run is on third.

These days, though, it’s more about fast pitching, long home runs and stolen bases. Bannister says that, along with the potential risk of injury, he’s concerned about a spiritual malaise. “We’ve now reached a saturation point where we’re vulnerable to squeezing the beauty out of the game, the storylines out of the game.”

Not everyone agrees. “There’s still plenty of art to the game,” says Tread’s Brewster. “It’s not purelyalgorithmic.” Friedman, the Pitching Ninja, says there’s never been a better time to be a pitcher. Eaton, the Rays’ surgeon, agrees. “You’re going to have opportunity coming your way,” he says. “Guys around you are going to be on injured reserve, and you’re going to have a chance show your stuff pretty soon.” Eaton envisions a future in which pitchers take the mound in wearable devices that might be able to predict when an elbow is at risk of blowing out. But we’re not there yet. And for the moment, he allows, it’s also a great time to be a surgeon.