Today’s MLB athletes play harder than ever, their bodies more explosive and precisely calibrated than those of any prior generation. With these gains in athleticism come heightened and more diverse injury risks. This past season, two former MVP frontrunners were sidelined with bizarre ailments. Mike Trout, at 27, developed painful Morton’s Neuroma. Christian Yelich fouled a ball so hard off his patella that it fractured. Thankfully, both should be prepared for the start of next season.

Not all injuries have simple recoveries. For as long as the sport has existed, athletes have been tearing the ulnar collateral ligaments in their elbows. The injury was codified under “dead arm” for most of the sport’s history until Dr. Frank Jobe performed a revolutionary reconstruction surgery in 1974. Jobe took a ligament from the non-pitching arm of all-star Tommy John and wove it through bone tunnels drilled in the elbow in a figure-eight fashion. The procedure extended the starter’s career by 14 years and 164 wins.

Other techniques now exist to treat UCL injuries, but none is known to be more effective than the “Jobe technique.” Still, despite the career-lengthening miracle of Tommy John surgery, recovery for pitchers is usually a process of at least a year.

UCL injuries have long been understood as a pitchers’ malady, but position players undergo Tommy John surgery, too, and have done so more frequently as players throw harder and harder. Current Twins manager Paul Molitor was the first position player to go under Dr. Jobe’s knife in 1984, and he appeared in 1,914 games afterwards. He was one of two MLB position players who had the surgery in the ‘80s, a number that spiked to nine in the ‘90s, 17 in the ‘00s, and 20 in this decade (including Aaron Hicks’ just-announced surgery). Tommy John surgery even loomed over the 2019 playoffs, bearing heavily over the performances of Didi Gregorius and Corey Seager, two star players whose teams were knocked out in the ALCS and NLDS, respectively.

Gregorius and Seager are distinct in many ways. Gregorius, the Yankees’ 29-year-old follow-up to Derek Jeter, is outgoing and open — he was eager to tell reporters how he had taught himself piano last offseason, for example. Seager, 25, seems much more reserved. But though separated by coasts, Gregorius and Seager are linked by the scars on their throwing elbows and their struggles to return to their pre-surgery career trajectories.

They reflect a blindspot in sports medicine: How does Tommy John surgery affect position players, and is it right to assume they can recover more quickly than a pitcher? Common sense says yes — their jobs are not as taxing on their throwing arms — but the sample size of position players who have come back from the procedure is so small it’s difficult to say what, exactly, a position player’s recovery from Tommy John should look like.

The only evidence available suggests that UCL injuries may affect position players more deeply than we think. And as the injury occurs more frequently, determining the truth is becoming more and more important.

Of the 1,814 Tommy John surgeries performed across all levels between high school and the majors, tracked by writer and analyst Jon Roegele, 90 percent (1,638) were performed on pitchers. The ratio is the same in MLB, where pitchers underwent 437 of 484 tracked Tommy John surgeries. Removing Pablo Sandoval and Salvador Perez, whose surgeries were performed this year, 45 MLB position players have undergone Tommy John recovery. One-fifth of those players did not return to the majors — most recently T.J. Rivera and Jason Coats, both of whom had surgeries in 2017 and spent this season languishing in the minors. Of the 36 position players who had Tommy John and returned to the majors, the average recovery time was just over 11 months.

Tommy John for position players is not quite the arduous, year-plus climb back it is for pitchers, but it’s still one of the most significant injuries that can occur in baseball. Dr. Frank Petrigliano — chief of the Epstein Family Center for Sports Medicine at Keck Medicine of USC, and former Los Angeles Kings head physician — has performed the surgery a number of times. He admits that, “the thinking on position players is still evolving.”

Petrigliano pushes back against a persistent myth that Tommy John is a “miracle surgery” from which players come back pitching harder than ever before. In truth, Petrigliano says, “it can take up to two years [for pitchers] to completely recover from a Tommy John surgery, and even longer than that to get back the velocity, accuracy, and action on the ball that they had prior to injury.” Petrigliano suggests physicians, likewise, often push position players to return before they should.

“The interesting thing with positional players is they have to hit as well,” Petrigliano says. “And if the injury is on the back hand, you know the elbow that sees the valgus force when swinging, they can have pain when hitting as well. So that surgery is not only affecting throwing and accuracy and velocity, but it can affect their hitting ability too, and I think that’s a little bit under-appreciated.”

It seems foolhardy to ask players to return to their regular production so soon after a career-altering injury, and yet that was what was expected of Gregorius and Seager this season.

Seager’s right elbow had been giving him issues for quite some time before he got surgery; he missed the 2017 NLCS in part due to an ailing elbow. Bone spurs and loose bodies invaded the joint, but at the beginning of the 2017-18 offseason they were believed to be better served by rest and management than arthroscopic surgery. Tommy John was only discussed in the abstract.

There is little definite knowledge of what causes UCL injuries in position players. The injury is still a relatively infrequent occurrence.

Dr. Petrigliano says the ligament is susceptible to overload, and that “players that throw more are going to have a higher susceptibility to injury.” Having pitched previously, even as an amateur, is a likely risk factor. Tommy John surgery is also more frequent among players who caught or played shortstop, positions that require a high volume of throws and are, from a young age, stocked by the players with the best arms. The correlation seems clear.

Seager’s UCL held up for less than a month in 2018. The pain recurred, more sharply than ever before, on a relay throw in April against the Giants. An MRI showed a strained, rather than torn, ligament, but Seager’s fate was sealed, and his timing unfortunate — the 26 games in which Seager appeared were his entire 2018 output. The then-24-year-old’s May 3rd surgery meant he would be shelved until 2019. The Dodgers claim Seager would have missed all of 2018 had he undergone surgery after the 2017 World Series, though Gregorius provides a rebuttal.

Greogrius harbored a partial UCL tear for years before the tendon finally snapped in a 2018 ALDS game against the Red Sox. By going under the knife on Oct. 17, 2018, however, the Bombers’ shortstop did not have the luxury of a lengthier layoff dictated by the season schedule. Whereas Seager went 11 months between appearing in games, Gregorius debuted on the June 7 of the 2019 season — less than eight months after surgery. Only three tracked position players have returned from the procedure faster.

Ten of the MLB position players who have undergone Tommy John surpassed 1.0 WARP — Baseball Prospectus’ catch-all player value metric, standing for Wins Above Replacement Player — during the season they had Tommy John surgery (or the season before, for those who had surgery before July). They averaged 3.1 WARP. Upon returning, the same group put up less than half their collective WARP before their injuries. Part of that dropoff is due to fewer plate appearances — position players who underwent Tommy John averaged 520 plate appearances before surgery, and just 341 during their recovery seasons. But those players also produced WARP per plate appearance at just two-thirds of their previous rate.

It seems evident that the degree of regression after Tommy John is starker than what might be explained by the time needed to shake off a long layoff. Ten players had a DRC+ — another Baseball Prospectus metric, which provides a context-neutral descriptor of a batter’s performance — at or above the league average of 100 the season before their surgeries, averaging 113. They averaged a 103 DRC+ the next season. Weighted for plate appearances, the 36 MLB position players who returned from Tommy John saw their collective DRC+ drop from 95 in one season to 93 the next.

Such an intensive procedure and long recovery should knock hitters off their groove; that the dropoff is more significant among higher-performing bats augments this theory.

In 2016, Seager’s first full season, and the only one unaffected by elbow issues, he recorded a 122 DRC+ (.877 OPS) on his way to a unanimous NL Rookie of the Year award and third place in MVP voting. It’s unclear how much a balky elbow harmed Seager during the 2017 regular season, but he fell off to 115 DRC+ and .834 OPS (a starker dropoff than it would appear in a boom year for homers). In 2019, Seager’s numbers dipped yet again: 106 DRC+ and .818 OPS. His WARP fell from 4.4 in 2016 to 3.1 in 2019, despite the fact that Seager improved dramatically on the defensive end.

The shortstop was the Dodgers’ two-hole hitter in 2017, but slotted in seventh during the 2019 playoffs. Seager took some of the blame for Los Angeles washing out in the NLDS, going just 3-for-20 across five games, striking out eight times and totaling a .390 OPS. Trade rumors have begun to swirl after the 2019 playoff exit — Seager’s second consecutive disappointing season and the team’s umpteenth.

For a while, things looked even more bleak for Gregorius. The 2018 season was arguably the best of Sir Didi’s eight-year career. Riding the best April in the bigs, Gregorius had career highs in homers (27), on-base and slugging percentages (.335 and .494), stolen bases (10) and WARP (4.4). Until his own ulnar collateral ligament popped, it seemed likely the then-28-year-old would earn a large extension or free agent contract.

After his 2019 season, the question now is whether the Yankees should keep their longtime shortstop around or put his salary ($11.75 million in his final arbitration season) to use elsewhere. Free agency looms after Gregorius had his worst season since the Bombers plucked him out of Arizona after 2014. In 344 plate appearances he was below-average with the stick (96 DRC+, .717 OPS), and he struggled defensively (mightily so, if you trust his minus-7.3 fielding runs above average). Gregorius has been a leader and a stabilizing presence in a turbulent half-decade by Yankees standards, but everyone knows that latest results matter in the Bronx.

At least, Gregorius and Yankees fans have reason to hope. After a hellacious September in which he posted a .627 OPS, raising the possibility that the Yanks might leave him off the ALDS roster entirely, the Dutch shortstop was one of the heroes in another drubbing of the Twins. Stepping to the plate with the bases loaded and his team staked to a 3-0 lead in Game 2, Gregorius hit a triumphant grand slam that sapped Minnesota of hope. The moment must have felt particularly gratifying for a player who has been forthcoming about his struggles this season.

“I’ve sucked, if you want the honest truth,” Gregorius said in September, via NJ.com. “I’m not where I want to be.” In the same article, manager Aaron Boone pointed out Gregorius’ recovery from Tommy John as a factor in his batting lines. Before the ALDS, GM Brian Cashman said the team knew “what he’s capable of” despite Gregorius’ underperformance, and after his game-sealing performance the 29-year-old spoke of how “the confidence level has got to stay up.”

The grand slam seemingly gave Gregorius a much-needed injection of positive energy, perhaps indicating a light at the end of an arduous recovery tunnel. Then he finished the postseason with a meager .478 OPS in six games against the Astros.

Tommy John has long been a pitcher’s bogeyman — it’s a ghost in many of their pasts and a hazy specter in the remainder’s future. Baseball players put their bodies on the line to a difficult-to-imagine degree. Take, for instance, CC Sabathia throwing three pitches after subluxing his shoulder.

We often fail to properly take pain into account when we judge athletes. They are always some combination of their talent, production, and personality, and rarely do we acknowledge the extent that the marvels and limitations of sports medicine form the foundation of our perception. Did you note Tommy John as you watched Seager and Gregorius struggle this season? Did their respective teams? Will its presence still be felt next season, and in their overall legacies?

And yet, those shortstops are lucky to play in an era when their careers could potentially be revitalized by a procedure that many have come to take for granted.

Gregorius shone, if only briefly, in the playoffs. For whomever he plays next season, all fans can hope is that the performance against the Twins was not an aberration. Or that the electrifying bat that Corey Seager flashed at 22 comes back. That despite their difficult recoveries and perhaps too-hasty returns, any position player struck down by UCL injuries has a chance to perform at their best on the sport’s biggest stages once again.

But that’s hope. All we know right now is that what we don’t know will continue to have an enormous effect on athletes who are fighting to be great.