FILE — In this April 5, 2007, file photo, San Antonio Spurs forward Tim Duncan (21) talks with Spurs coach Gregg Popovich, left, during the fourth quarter of their NBA basketball game against the Phoenix Suns in San Antonio. (AP Photo/Eric Gay, File)

SHARE (FILES) This file photo taken on April 28, 2015 shows Chris Paul of the Los Angeles Clippers as he shoots under pressure from Tim Duncan (R) of the San Antonio Spurs during Game 5 of their first round NBA playoffs series in Los Angeles, California San Antonio Spurs star forward Tim Duncan on July 11, 2016 announced his retirement after 19 season in the NBA, a glittering career that included five National Basketball Association championships and 15 All-Star Game appearances. / AFP PHOTO / FREDERIC J. BROWN/AFP/Getty Images

By Mark Travis

The one virtue neither Father Time nor his troublesome knees could ever take from Tim Duncan was his presence.

Whether it was on the floor or in the locker room, Duncan's endearing and selfless disposition defined a franchise for nearly two decades and provided the framework for one of the most dominant dynasties in the history of sports.

Even as his numbers dwindled, his playing time shrunk and the rest of the league evolved while his athleticism declined, Duncan's presence carried the San Antonio Spurs for 19 consecutive seasons.

On Monday, Duncan decided 19 seasons was enough.

It speaks to Duncan's immense value that his retirement has sent shock waves across the NBA despite years of Groundhog Day-like anticipation. This offseason the whispers never left much room for optimism, with all reports indicating Duncan was as close to the exit door as ever. But even if it is written in stone, nothing prepares a team, league or fan base for the day when a legend like Duncan walks away.

What makes Duncan's departure so impactful is what his presence always guaranteed the Spurs: Success.

Duncan made the playoffs every year of his career and won 50 or more games in 18 of his 19 seasons, with the lone exception being the lockout shortened 1998-99 season, a season the Spurs won the title. He was the anchor of the winningest trio in NBA history alongside Tony Parker and Manu Ginobili, and no player-coach duo has ever won more games than the 1,001 Duncan and Gregg Popovich won together. And Duncan retires after the best regular season in Spurs history, during which they won 67 games and tied the NBA record with their 40-1 record at home.

Although they didn't stand out because of the Spurs' brilliant play, there were signs during the season that this would be Duncan's last year. He missed eight straight games in January and February because of an injured right knee and never looked quite as spry once he returned. The Spurs were unquestionably better when Duncan was off the floor against the Warriors, which might have led to Duncan coming off the bench in the conference finals if the Spurs had advanced that far.

That said, Duncan's retirement seems a season premature. He was legitimately good last season. His offensive numbers hit a career low, but that was expected with LaMarcus Aldridge's arrival making him the fifth option. On the other end, Duncan remained superlative, posting advanced numbers that gave him an even stronger case for the Defensive Player of the Year award than Kawhi Leonard, who won the award for the second straight season. But rather than pushing for a 20th season when his knees might have prevented him from being a positive contributor, Duncan finishes his career having helped the Spurs to the very end.

And though Duncan finished his career as a defensive specialist, lest we forget, prime Duncan was one of the most incredible all-around basketball players in the history of the NBA. Duncan averaged 21 and 12 the moment he arrived in the NBA and there wasn't a single basketball skill he didn't possess. He was fluent, if methodical, on the block, a cunning passer from his perch in the post, precise with his finishes, deliberate in cleaning the glass and punitive when protecting the paint.

Duncan's unprecedented longevity elevated him to a different historic pantheon, but the player he was before he began passing the torch put him in position to be an all-time great. When it came time to take a back seat, Duncan was more than accommodating, constantly seeking to reinvent himself, always looking to bend and twist to perfectly suit the needs of his team.

It is hard to shake the idea that the modern Bill Russell just retired. From his unparalleled defensive ability to his genius understanding of the game to his reputation as the best teammate in the NBA, Duncan's résumé mirrors Russell's, and Duncan did his winning in a much more competitive era. With five championships, three Finals MVPs, two regular season MVPs and 19 years of stability for his franchise, Duncan has a strong claim as the best player of his generation and as one of the five best players in NBA history.

Duncan does not leave the Spurs in a vulnerable state. No team other than the Warriors is set up for future success better than the Spurs are with Leonard as their next franchise cornerstone, and San Antonio should still be Golden State's biggest threat in the West during the next couple of years.

But as great as Leonard, Popovich and General Manager R.C. Buford are, the Spurs will not win 50 games a season for the next two decades, they will not make the playoffs for the next 19 seasons and they won't hang five more championship banners in the rafters by the time Leonard turns 40.

They won't because the presence of Tim Duncan, a player whose fusion of humility, class, and ability will never be replicated, made all of those things possible.

And now Duncan, seemingly forever present, is in the past.