Kevin Durant expects to live to 100. Asked recently why he is so sure he’ll reach the century mark, he raised his eyebrows, shrugged and shot back: “Why not?”

By that measure, Durant — less than two weeks removed from his 30th birthday — is nowhere near middle-aged. The life span of an NBA career, however, forces most 30-year-olds to consider their professional mortality.

It is an important reality for the Warriors, whose four core players — Durant, Stephen Curry (30), Klay Thompson (28) and Draymond Green (28) — are at or near age 30. To guarantee long-term success, Golden State must keep those four together and ensure that they defy conventional wisdom, playing at an All-Star level well into their 30s.

With that in mind, the Warriors hired Rick Celebrini — a master at helping athletes push the limits of their prime — as their director of sports medicine and performance in August. Celebrini boasts an impressive resume that spans the NBA, NFL, NHL and even the Canadian men’s alpine ski team, but it was his work with Steve Nash that made him Golden State’s top choice.

In March 2015, when Nash announced his retirement from the NBA in an article on the Players’ Tribune, he wrote that Celebrini “had as big an impact on my career as anyone.” It was hardly hyperbole. Thanks largely to Celebrini’s correctional exercises, Nash played his best basketball after he turned 30.

His two MVP awards came when he was 31 and 32. Between 33 and 35, Nash finished three seasons in the 50-40-90 club (50 percent from the field, 40 percent from three-point range and 90 percent from the foul line). At age 35, he led the Suns to the Western Conference finals. By the time Nash made his eighth and final All-Star appearance in 2012, he was 38.

“I think Rick’s experience working with elite athletes in a unique way is really going to benefit our guys, especially our guys who are getting close to 30,” Golden State head coach Steve Kerr said. “They’re entering that stage of their career where they’ve got to start paying extra attention to their bodies, and their preparation and recovery. That’s really part of Rick’s expertise.”

Nash, like Curry, wasn’t the type of point guard who set bench-press records or threw down highlight-worthy dunks. What made him effective was his core strength, balance, hand-eye coordination and ability to change direction quickly.

While with Dallas early in his NBA career, Nash hired Celebrini — a former soccer player and physiotherapist from Nash’s native Canada — to help him manage his spondylolisthesis, a spinal disorder that causes severe lower-back pain.

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Celebrini, who was not made available for this story, taught Nash how to economize his physical movements. Their sessions together were so effective that in July 2004, after Nash signed as a free agent with the Suns, he flew Celebrini to Phoenix. Twice a day for six weeks, Celebrini put him through workouts designed to fine-tune his balance and agility.

After one such session that Kerr, then a consultant with the Suns, met Celebrini at the team’s practice facility. Impressed by Celebrini’s innovative techniques, Kerr peppered him with questions about his background, influences and aspirations.

This July, when head performance therapist Chelsea Lane left the Warriors after three seasons to take a similar position with the Hawks, Celebrini’s was the first name Kerr considered as a possible replacement. When the team contacted Nash — a consultant with Golden State — to gauge Celebrini’s interest, Nash said, “Probably not, but you can ask him.”

Celebrini, who was working in British Columbia for the NHL’s Vancouver Canucks and Major League Soccer’s Vancouver Whitecaps FC, hadn’t been looking to move. However, the chance to help Curry, Durant, Thompson and Green navigate the next stage of their careers intrigued Celebrini too much to say no.

“You get past 30, it’s hard. You’ve got to continuously work out,” Thompson said. “You just have to be more meticulous with your training and realize the end is not near, but it’s sooner than later.”

To better understand how to help Curry, Durant, Thompson and Green, Celebrini has spent portions of training camp observing how each All-Star moves. Once he understands their tendencies, he can work on slowing down the aging process.

Because even though the four stars are still at the peak of their powers, they’re far from immune to the toll of time.

Hobbled by knee and ankle issues, Curry was limited to 51 games last season, his fewest in six years. Durant, who has led the league in minutes three seasons, is beginning to notice that it’s taking him a bit longer to recover from games.

Though Thompson has built a reputation as an iron man of sorts, even he has started making a point to eat healthier and maintain a regular offseason workout regimen. Part of the reason Green wasn’t as dominant defensively last season was because he dealt with nagging pain in his shoulder, knee and hips.

“When we hired (Celebrini), Steve (Nash) called me right away and told me how much he’ll help me as a player,” Durant said. “He’ll have me think about the stuff I never thought about from a movement perspective, activation of muscle.

“I think it’s perfect timing for me, and for all of us, really.”

Connor Letourneau is a San Francisco Chronicle staff writer. Email: cletourneau@sfchronicle.com Twitter: @Con_Chron