Mark D. Smith-USA TODAY Sports San Antonio Spurs center Tim Duncan (21) fights for position with Oklahoma City Thunder center Steven Adams (12) during the first quarter in game six of the second round of the NBA Playoffs at Chesapeake Energy Arena.

SHARE EPA/LARRY W. SMITH San Antonio Spurs' Tim Duncan (L) goes to the basket and is blocked by Oklahoma City Thunder's Steven Adams (R) in the first half of the NBA Western Conference semifinal Game 6 at the Chesapeake Energy Arena in Oklahoma City, Oklahoma. San Antonio Spurs center Tim Duncan (21) in the second half of an NBA basketball game Friday, April 8, 2016, in Denver. The Nuggets won 102-98. (AP Photo/David Zalubowski)

By Mark Travis

The setting, the circumstances, the pupils were different, but the symbolism was the same.

In 2007, Tim Duncan and LeBron James crossed paths in the corridor of Quicken Loans Arena, with Duncan dawning a championship shirt that was a half-hour old.

"This is going to be your league in a little while," Duncan famously told James, "but thanks for giving us this year."

On Thursday night, Duncan's hand patted the chest of another burgeoning legend, this time at center court at Chesapeake Energy Arena in Oklahoma City. Duncan had parting words for anyone who lined up to pay respects after the Thunder upset the Spurs before arriving at Kevin Durant.

Duncan's message to Durant was probably similar to what he told James: The NBA, and maybe even his place on the Spurs, was Durant's for the taking.

Moments later, Duncan raised his hand and pointed a finger to the sky, acknowledging a raucous Thunder crowd that reverently returned the favor, before slipping off into the tunnel for possibly the last time.

Another torch had been passed. Or so it seemed.

Had Duncan called it quits after he collected his fourth ring against the Cavaliers at 30, he would have retired the greatest power forward to ever play. Instead, he has added nine 50-win seasons, three 60-win seasons (including a franchise-best 67 wins this season), four conference finals appearances, two trips to the Finals and another ring during the back half of his career.

Duncan's postscript to his prime lasting nine seasons and including unprecedented team success is just as impressive as the days when he was a walking double-double and obvious MVP candidate. Duncan had defied decline for so long that it seemed assured that he would retire without ever looking vulnerable. Against Oklahoma City, with the young and athletic trio of Serge Ibaka, Steven Adams and Enes Kanter protecting the paint and battering him on the boards, Duncan finally looked his age.

Never had the inevitable seemed so surprising.

Duncan's deterioration against Oklahoma City wasn't a unique problem. As Duncan missed shots in the paint he used to make in his sleep, Manu Ginobili struggled to create separation and to stay in front of the Thunder's swarming perimeter players, David West and Boris Diaw were abused on the glass and even LaMarcus Aldridge was physically worn down by the end of the series.

The only Spurs who looked as if they belonged athletically in this series were Danny Green and Kawhi Leonard. As was the case in 2012, the Thunder exposed San Antonio with an attribute nobody can control: Youth.

With athletic superstars such as Westbrook and Durant entering their primes and a fast-paced, small-ball dynasty brewing in the Bay Area, Duncan and Ginobili will have to decide whether prolonging their Hall-of-Fame careers is a shrewd decision. Duncan and Ginobili can still be effective contributors in a pinch, but the league is quickly trending in a different direction.

For Duncan, retiring at 40 is a natural stopping point, but coming back for his 20th season with one team like his old rival Kobe Bryant just did would be fitting, too.

If this is the end for Duncan, he leaves having done everything in his power to maintain the Spurs' dominance during his 19 seasons. He did every job asked of him, from superstar anchor on both ends of the floor in his prime to the guiding light for San Antonio's next generation during his epilogue, and his myriad accomplishments and accolades will land him on almost every list of the 10 best players ever.

The nine-season gap between Duncan prophesying James' dominance and his congratulatory embrace with Durant might be Duncan's greatest achievement. Duncan, who won a title in three different decades, defined a dynasty that survived a generation past its expiration date, prolonging the waits of Durant, Westbrook and many others to supplant the Spurs as the next powerhouse in the West.

And if Duncan walks away, he does so having left the Spurs with one final triumph: A sturdily built bridge to Spurs' next era.

Duncan lasted long enough to watch Leonard grow into a perennial MVP candidate, and his allure was great enough to attract Aldridge in free agency, giving San Antonio a strong foundation to build on when he is no longer around. Although Duncan might have told James and Durant the league would soon be theirs, he has helped groom his own heir apparent in San Antonio, ensuring the torch at the AT&T Center will stay lit.

Because the Spurs, like Duncan, will never go away.