Tyrese Haliburton tried to heal his right calf strain in time for the biggest game of his life, Game 7 of the 2025 NBA Finals.

Multiple hyperbaric chamber sessions per day. H-Wave electrical stimulation. Treatment around the clock. All that seemed to work. The opening minutes of Game 7 became The Tyrese Haliburton Show. The two-time All-Star sank three straight 3-pointers to pull the Pacers ahead 14-10. To the undiscerning eye, his calf seemed just fine.

And then, the show ended.

At the five-minute mark in the first quarter, the largest tendon in Haliburton’s body snapped as he pushed off his right heel to accelerate forward. His worst fears were realized: an Achilles tear proximate to the same damaged right calf. He pounded the hardwood in disbelief. With Haliburton sidelined, the Thunder pulled away late and won by 12.

Hunched on crutches in the hallway after the game, Haliburton greeted his teammates and was met with hugs and tears. Little did we know, his injury didn’t just disrupt the 2025 NBA Finals; it also disrupted the entire NBA landscape. Like an earthquake that sends shockwaves for months, Haliburton’s torn Achilles that was preceded by a calf strain — on top of the Achilles tears of Damian Lillard and Jayson Tatum in the injury-marred 2025 postseason — fundamentally changed the way teams are operating this season. And not just the Pacers, who have fallen to 6-18 without their star.

Ja Morant. Victor Wembanyama. Giannis Antetokounmpo. All suffered calf strains in the opening weeks of the season. All sidelined for multiple weeks. They are the biggest names, but there are more. A lot more. In the first 20 games of the 2025-26 season, we’ve seen a substantial increase in calf injuries (excluding contusions caused by blunt force), according to leading injury expert Jeff Stotts of InStreetClothes.com. This time last season, there were 18 calf injuries at the 20-game mark. This season, it’s up to 25 incidents, representing an increase of nearly 40%.

More significant, however, is the elongated recovery timeline of these injuries. Per Stotts’ data, the number of games lost due to calf injuries, through 20 games played, skyrocketed from 36 to 108. A tripling of last season’s total.

Luka Dončić was traded, in part, because of his recurring calf strains in Dallas. Antetokounmpo may be the next example, as the NBA world tries to decipher how his recent history of calf strains will affect his future. No one wants to have another Haliburton situation, most of all, the players.

Something has changed. But pinpointing exactly what is a mystery that has perplexed NBA teams, fans and the medical community.

Based on the injury data and conversations throughout the league with Yahoo Sports, these have become the two scariest words in basketball:

Calf strain.

Dr. Richard Ferkel is a top orthopedic surgeon at the Southern Orthopedic Institute and an assistant clinical professor of orthopedic surgery at UCLA. He has operated on over a dozen Achilles tears of NBA players, including Klay Thompson, DeMarcus Cousins and Rodney Hood. In February, Thompson presented Ferkel with a 2022 NBA championship ring as a thank you for stitching his Achilles back together and allowing him to somehow be, in Thompson’s own words, the second-best scorer on a championship team.

Thompson’s trust in Ferkel is shared by the league office. Ferkel serves as a medical consultant at the annual NBA Combine regarding lower leg issues. He is also a key member of a medical committee that the NBA assembled this summer, staffed by leading surgeons, PhDs and researchers who convene to study the recent uptick in lower leg injuries. They meet periodically over Zoom to discuss, among other topics, the hottest medical issue in the league right now: searching for answers about the rise of calf strains and its possible relationship to the spike in Achilles tears.

Teams are being much more conservative in returning players back from calf injuries.Dr. Richard Ferkel

Ferkel sees a lot of caution across the sport.

“There is a concern that calf injuries can lead to Achilles injuries, and that this is all due to incomplete rehab in the calf and favoring one leg over the other,” Ferkel said. “Teams are being much more conservative in returning players back from calf injuries.”

Making sure players are fully recovered from calf injuries is a challenge when the game is being played faster than it has in decades and the NBA has added back-to-backs (about two more per team compared to 2019-10) to the schedule in order to accommodate the in-season tournament, which has a title sponsor in Emirates Airlines. The task of balancing economic and medical constraints is not an easy one.

“I think the increased speed of the game, increased athleticism, increased demands of the schedule all contribute to these problems,” Ferkel said.

The solve can’t come soon enough as flat tires continue to sideline players. Ferkel notes that Achilles injuries seem to be down this season, but calf strains are up considerably. It should be mentioned that former All-Stars Dejounte Murray, Lillard, Tatum and Haliburton along with three other players, for a record-setting total of seven players, are still out with Achilles tears from last season and it’s not clear when they will return. Teams will be paying those four All-Stars a collective $200 million in this season alone.

“The NBA is very concerned,” Ferkel said, “as are all doctors.”

Could the injuries have been prevented?

Like many Davidson alums, Dr. Scott Ellis of the Hospital of Special Surgery (HSS) in New York has become a huge NBA fan thanks to fellow alum Stephen Curry. Over the years, Ellis has performed calf, foot and ankle repairs for NBA athletes, though not to the extent of his colleague Dr. Martin O’Malley.

If Haliburton and Tatum win championship rings in the future, they might give their hardware to O’Malley, or “Marty” as he’s known in the sport. He is a foot and ankle surgeon at HSS and is also the team surgeon for a host of sports teams, including the Brooklyn Nets, New York Giants and USA Basketball. When I talked to HSS for this story, they referred me to Ellis, who doesn’t work for an NBA team and can speak more freely about the increasingly pressing issue.

Speaking over the phone, Ellis expressed an acute sense of urgency regarding the rise of Achilles tears and calf strains. Bodies keep breaking down. Billions of dollars are tied up in TV contracts, salaries and franchise values. Everyone’s searching for answers.

“Managing expectations and outcomes is not easy,” Ellis said, “because the money at stake is so high.”

In Ellis’ eyes, the foot and ankle injuries we’re seeing in the NBA now are overuse injuries due to the demands of the schedule. Typically, the common injuries in the league were stress fractures or navicular fractures in the foot from all the pounding amid 82 games. But nowadays, calf strains and Achilles tears are popping up far more frequently — especially in younger athletes.

“What's really amazing is you think about the Achilles injury, it usually happens to the Weekend Warrior — older people who aren't as active,” Ellis said. “They go play sports on the weekend, all of a sudden, they rupture their Achilles. Usually it comes out of the blue with no symptoms.”

Kevin Durant’s Achilles tear in the 2019 NBA Finals stuck out to Ellis for two reasons. One, his age. He was 30 when he tore his Achilles. That seemed to be young. But Tatum was 27 when he tore his. Haliburton was 25. His Pacers teammate and former No. 2 overall pick, James Wiseman, was 23.

“The rash of this happening in younger professional athletes is definitely new,” Ellis says.

Durant’s Achilles rupture also was alarming to Ellis because of what came before it: a calf strain. In his decades of practice, a calf strain wasn’t a typical precursor to Achilles tears.

“The interesting thing is, historically, a calf strain is thought of as this completely separate injury from an Achilles tear,” Ellis said. “When you have somebody with an Achilles rupture, nine times out of 10 — actually, even more, 99% of the time — they don’t have anything that you could pick up structurally in an imaging exam on their Achilles.”

The spreadsheets on Stotts’ laptop point to a similar conclusion, one that raises lots of thorny questions for medical teams around the sport. In Stotts’ database, he has logged over 400 calf injuries, but he could find only two instances of calf injuries that directly preceded a torn Achilles. Both happened in the NBA Finals: Haliburton in 2025 and Durant in 2019.

That both instances came on an NBA Finals stage may not be a coincidence. It’s easy to see how risk tolerance would be extraordinarily high given that championship glory is within arm’s reach. For the greats, a short-term chance at immortality is worth risking long-term ruin.

Hundreds of players have played deep into the NBA season without tearing their Achilles. But Haliburton’s high-profile tear and the spate of calf injuries to star players speaks to something larger, suggesting that something has transformed outside of the human anatomy.

“The game has definitely changed,” Ellis said. “I’m a Steph Curry fan, but I think he changed the game.”

To an uninformed spectator, Curry would seem to be standing at the top of the key facing the basket. Curry is thinking differently. In the mind of the greatest shooter ever, he imagines he is looking down from the gym’s rafters, planted at the epicenter of an imaginary clock. The rim is six o’clock. The half-court directly behind him is 12 o’clock. To his right is nine. To his left, three.

It’s the summer of 2013, and Curry thinks this clock and this drill has a chance to change everything. He’s not yet an All-Star, but he’s made the leap as the Warriors’ leading scorer. There are more leaps to make. All-Star, maybe MVP. Hopefully, NBA champion. That’s the vision.

Danny Green and Kawhi Leonard made him go back to the drawing board. Curry and his longtime trainer, Brandon Payne, had watched film of the 2013 playoffs and how Spurs coach Gregg Popovich had put taller wings on Curry to block out any sunlight on the perimeter. The Spurs had beaten the Warriors soundly in the second round. Curry needed to reinvent himself.

“That’s where it all changed,” Payne said.

They called it Lego space creation. Payne and Curry put two or three footwork concepts together to create necessary space to get the shot off based on what the defender does. That whole summer, Curry worked the clock in various gyms, adhering to Payne’s orders as he shouted different numbers.

“Twelve!” Payne blurted out.

Curry stepped backward. Shot.

“Twelve to nine!”

Curry stepped back and then right. Shot.

“Six to 12 to four!”

[Haberstroh: The NBA star crisis worsens]

Over time, Payne added hybrid moves to shift to certain spots like they were sweating through a game of Twister. If the goal is to get to 12 o’clock, Payne would shout a combo move — say, 10 o’clock to two o’clock — in order to juke the imaginary defender enough to eventually plant both feet, both hands in a 12 o’clock spot.

“If you’re looking at the face of a clock,” Payne said, recalling those countless sessions in the gym, “we wanted to make sure we could create space going to every single number on the clock.”

The key, he said, is that Curry’s trainers would load the movement with resistance bands and heavy lifting in order to properly strengthen Curry’s muscles to execute the new motion patterns. He had to prepare his body to perform.

And so Curry decided to implement the stepback and side step. No longer are players training to do set shots and pull-up jumpers in front of them. To combat the growing size and athleticism of defenders, scorers like Curry are forced to go in reverse and sideways in ways never thought possible.

To illustrate the evolution, consider that in 2013-14 Curry led the league with 69 stepback 3s, per Kirk Goldsberry’s tracking. Two MVP awards and three NBA championships later, the league started catching on to Curry’s innovative moves. By 2018-19, the league leader in stepbacks, Houston’s James Harden, registered 613, a tenfold increase in just five years.

Were we thinking at the time, well, the NBA is going to have a lot of calf and Achilles issues? No, we were not thinking that at the time.Brandon Payne, longtime trainer

Stephen Curry spawned a league full of people trying to be Stephen Curry — no matter if they’re 6-foot-2 like Curry or 7-5 like Victor Wembanyama, who averages over six 3-point attempts per game in his NBA career, many of which are hitting different numbers on the clock. Everyone wants to be Steph, but a separate question is whether their bodies are equipped to handle it.

Dončić, Haliburton, Lillard and Tatum are some of the most innovative creators when it comes to getting to their 3-point shot and using counters to attack the threat of the deep ball. The longer 3-pointers also mean longer runways, which require stronger brake systems to decelerate and finish at the rim after going downhill. And they all use “false steps” to accelerate forward with a push-off on a back foot and take advantage of hard closeouts on their 3-point shots. Is it a coincidence that they’re beset by calf and Achilles issues?

Looking back, Payne didn’t consider the long-term implications of the clock drill. But like many others around the league, he wonders about how the game has changed, the role of the 3-point shot and whether it’s a factor in what we’re seeing.

“Now, were we thinking at the time, well, the NBA is going to have a lot of calf and Achilles issues? No, we were not thinking that at the time,” Payne said.

The race to solve the issue isn’t just a medical one. It’s being waged in Silicon Valley.

Brett Burman thought there had to be a better way. After working in NBA front offices for over a decade and leading the London Lions to the 2023 EuroCup Final Four as the team’s general manager, Burman understands why so many teams are terrified of non-contact injuries.

He left London in 2023 with a basketball executive’s version of what he calls “PTSD.” After signing three former NBA players to key roles, he watched them go down with major non-contact injuries. Sam Dekker, Tarik Phillip and Kosta Koufos all suffered key injuries that ruined the team’s chances of reaching its potential.

He remembers going into a hallway and FaceTiming the team doc about whether to let Dekker back into the game or keep him out. In a matter of seconds, they had to make the call.

“And we made the wrong one,” Burman says. “I had the players’ health — he was tough as s*** — and the weight of the whole organization on my shoulders. I didn’t have the data, the science, and we made the wrong decision.”

Following that experience in London and all his years in the NBA front office, Burman linked up with Adam Petway, the former director of performance of the Washington Wizards, and founded a new company called OnSport AI that tries to revolutionize injury prevention in pro sports. One NBA team has signed on as they pilot their software, and they are in talks with several other teams for their services.

OnSport AI uses computer vision and machine learning fused with tracking data to identify injury risk in real-time during competition. The company’s software tracks coordinates for joints — think hips, ankles, shoulders, elbows, etc — for all 10 players on the court and compares it to each players’ historical record going back years thanks to TV broadcasts.

How did that player jump? Off one foot or two? How did they move laterally? How did they land? Are their hips level or favoring one side? In laymen’s terms, OnSport AI seeks to detect if something in a player’s biomechanics is “off” and alerts the user when risk of injury reaches certain thresholds.

Picture, for instance, instead of a stamina meter above a player in video games, the screen shows a color-coded injury risk meter that quantifies a player’s likelihood of suffering a non-contact injury based on their proprietary system.

Burman’s company and other tech outfits are racing to solve the problem. On Tuesday, leading data provider Sportradar and bio-analytics company Orreco announced a brand new player health and data-tracking partnership that promises to “maximize availability” and track workloads in a similar manner as OnSport AI. In January, the NBA announced it was launching a new biomechanics program to try to reduce injuries in light of the uptick in player absences. Four companies were selected to collaborate with the NBA in consultation with P3, a leading sports science lab in Santa Barbara led by Dr. Marcus Elliott.

Henry Abbott’s new book “Ballistic,” which profiles Elliott and his leading work in injury-prevention science, could be described as a 300-page ode to our hips. So much of the ailments in the NBA athlete can be traced back to irregularities in the hip and how it absorbs and facilitates the ever-expanding, thunderous forces in the game.

It shouldn’t be a surprise to learn, then, that Curry worships at the altar of hips. In 2015, the Warriors’ then-director of athletic performance Keke Lyles told me Curry, the smallest guy on the team, was second strongest on the team in the deadlift category, regularly lifting 400 pounds. To improve flexion and mobility, he obsessed over exercises like the single-leg hip airplane yoga move.

Strengthening his hips was the key to saving his ankles that had hampered him early in his NBA career. (So did Ferkel’s surgical procedures.) Notably, Curry, who has weaponized the 3-ball more than anyone, has not been listed with a calf strain or Achilles injury in his 17-year career.

One of the key indicators for OnSport AI’s technology focuses on the coordinates of the ball-and-socket joint, the hip. The exact patterns they flag in hips and other body parts are tightly guarded; Petway and Burman call it their secret sauce, honed through thousands of hours in NBA circles and poring through the literature. The false step, it turns out, is a central character in Petway’s published research on Achilles tears, but identifying the underlying cause of Achilles ruptures is more nuanced. The false step — the action that befell Haliburton, Lillard and Tatum — could be better described as the straw that broke the camel’s back, but not necessarily deserving of the most blame.

Putting aside the medical concerns, good luck getting rid of the false step in basketball. Convincing elite hoopers to change their instinctual movement patterns is a daunting task. Perhaps even more challenging is getting sign-off from the National Basketball Players Association to track real-time injury risk using fancy algorithms with team staffers at the controls.

In June, Adam Silver said on ESPN that the league was using artificial intelligence to get to the bottom of it and it's formed panels to address it. The addition of cutting-edge technology and the formulation of committees could dramatically improve the issue of calf strains and Achilles tears. It could also be years before conclusions can be drawn, and even longer to be implemented at scale. Time is of the essence. Within six months of the NBA launching the biomechanics tech initiative in January, the world watched as three of the biggest names in the sport — Tatum, Lillard and Haliburton — went down with Achilles tears.

But one subtraction could help — and fast.

The looming variable over all of these lower leg injuries is, of course, the 82-game schedule that has been in place for nearly 60 years.

It’s a contentious issue that requires all stakeholders — owners, players and TV partners — to come together and reevaluate the entire system. With the 3-point arc stretching the dimensions of the game further and further out, the game is much more demanding. Steve Kerr raised concerns to Yahoo Sports this past May in the wake of so many high-profile injuries.

Dr. Ferkel saw Kerr’s quotes and made note of his remarks in our discussion about the current issues. When I asked Ferkel if he thought the league should reduce the number of games in the schedule to increase the number of recovery days, he said it’s something that comes up frequently.

“We’ve discussed this at length, regarding limiting the number of games in the schedule, especially back-to-backs,” Ferkel said. “The league is looking at this carefully and they’re trying to find data to explain if there is a relationship between back-to-backs and injuries.”

What is his view?

“I feel there may be a relationship, but we need more science to know for sure,” Ferkel said.

Over at HSS, Ellis shares the sentiment that reducing the number of games could be a solution, if the economics can be worked out. He points out that the economics might not be working for fans now.

“It’s a huge number of games that they're playing, day in and day out, some back-to-back,” Ellis said. “We've seen coaches resting their players and then the league gets on them because people are paying tickets to watch these players. Something has to give.”

Too often recently, everyone agrees, that something is the Achilles tendon.

Ellis comes back to Curry and how the game is being played now. The speed of the games. The speed of the schedule. Tatum, Lillard and Haliburton were three of the top 3-point shooters in the game, all suffering Achilles tears in big moments. Can we really eradicate the 3-point shot and how they get to those shots?

“I wouldn't say a stepback by itself is like a major trauma,” Ellis said. “But maybe they're doing it over and over and just … it's stretching the limits.”