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Basketball is a young man's game, but the rules have never seemed to apply to Tim Duncan.

Though incoming rookies on the San Antonio Spurs might be tempted to ask him what it was like to invent fire, then wonder how difficult it was to bank jumpers into a peach basket, Duncan still isn't too old to star in the NBA.

The iconic big man has been working on his craft for quite a long time. Now 39 years old, he was drafted out of Wake Forest with the No. 1 pick in 1997, and the rest is history. He's racked up a ridiculous number of accolades during his time in the Association, thriving from both an individual and team perspective during his 18 seasons of professional basketball.

But this isn't about the honors he's earned or the titles he's won. Kobe Bryant gets so much attention now that he's moving into what could be the final season of his career, but Duncan deserves just as much. It's an indisputably remarkable fact that Duncan is still going strong as he enters what could be his own last go-round playing for the Spurs.

Precious few throughout the history of the league have been able to claim this type of longevity.

Just 13 players, in fact, and not many of them have come close to matching the levels of their earlier exploits, as Duncan is likely to do during the 2015-16 campaign:

The Rare 19th Season Player Year Games Played Season PER Career PER Kareem Abdul-Jabbar 1987-88 80 15.8 24.6 Moses Malone 1992-93 11 18.7 22.3 Robert Parish 1994-95 81 10.1 19.2 James Edwards 1995-96 28 3.5 14.7 John Stockton 2002-03 82 21 21.8 Charles Oakley 2003-04 7 8.1 13.4 Kevin Willis 2003-04 48 14.9 15.7 Karl Malone 2003-04 42 17.8 23.9 Shaquille O'Neal 2010-11 37 17.4 26.4 Juwan Howard 2012-13 7 9.9 14.6 Jason Kidd 2012-13 76 13.5 17.9 Kevin Garnett 2013-14 54 13.3 22.8 Kobe Bryant 2014-15 35 17.6 23.2 Basketball-Reference.com

Of the 13, only Kareem Abdul-Jabbar, Robert Parish, John Stockton, Jason Kidd and Kevin Garnett were able to stave off injuries and carve out a large enough role in their teams' rotations to suit up in 50 contests. Among that quintet, though, only Stockton and Abdul-Jabbar played like they weren't feeling the ill effects of Father Time; the other three were shells of their old selves.

Take a wild guess which category Duncan will fall into, given that his per-minute numbers have remained so eerily consistent throughout his career. Duncan's player efficiency rating since 1997 stands at 24.5, and his 2014-15 mark was still a stellar 22.6.

Nothing about the trajectory of his career indicates that he's due for a steep drop-off:

Though his PER has been trending down slightly in recent years, that all-inclusive metric is still hovering at an elite level. As for the dip in scoring, that's only natural as he dials back that facet of his game and allows Kawhi Leonard to continue asserting himself as an offensive leader. Chances are it will decline even more now that LaMarcus Aldridge has joined the Spurs, though that's by no means an indictment of Duncan's skills.

This future Hall of Famer is set to do the impossible: play out his 19th season in the Association as an enduring star in the frontcourt. Stockton, for example, didn't have to lug around nearly as much weight when he was finishing up his second decade of professional ball.

As a result, Duncan is poised to venture into territory we've never seen before. Records for a player this deep into his career are about to fall with alarming frequency.

First, rebounding:

The mark to beat is a mere 478—a total toppled by Duncan during each and every season of his illustrious career. Even during the 2014-15 campaign, his 18th, he managed to haul in 704 boards for the Spurs, leaving little doubt that he should be able to dethrone Abdul-Jabbar with relative ease.

If we assume Duncan plays in just 70 games—even though he's hit 74 and 77 during the last two campaigns, respectively—he'd need to average just 6.8 rebounds per contest in order to get there. Considering the worst average of his career is 8.9, we'll leave you to draw your own conclusions.

But how about in the scoring column?

Though Bryant was averaging 22.3 points per game when he was shut down for the season, a mark that should be viewed as just about untouchable for a player so far into his professional career, the total scoring record still belongs to a different member of the Los Angeles Lakers.

For Duncan, this one is going to be tougher to break.

If we continue assuming he'll suit up in only 70 contests, he'd need to average 16.6 points per game, a figure he hasn't hit since 2012-13. Given the improvements of Leonard and the arrival of Aldridge, it would be incredibly unlikely for him to turn back the clocks in that fashion. After all, we know the younger power forward isn't going to take a massive step back in the scoring column.

"I was like, 'If y'all want me to come here and average 12 or 13 points, that's not who I am. I like scoring.'" Aldridge told USA Today's Sam Amick about his decision to join the Spurs over the Phoenix Suns. "They were like, 'No, we want you to play in the system, but you [sic] scoring is needed here.' Once I heard that, I was fine."

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With that in mind, if Duncan makes 77 appearances, as he did last season, the necessary average for the record will drop to 15.1. That may still be out of reach, given the fact that he posted 13.9 points in his typical outing last season, but there's no denying he has the skills needed to up the figure once more.

Even if Duncan falls short of Abdul-Jabbar, he's still a near-lock to cement the No. 2 spot on the 19th-season leaderboard. At the very least, he'll become the fifth player in NBA history to average double digits at this advanced stage.

Plus, there's another category in which he figures to move up to the top of the pack.

Only once in Duncan's entire career has he failed to record triple-digit rejections, and that was during the lockout-shortened 2011-12 campaign. Even that year, he managed to swat 88 shots in just 58 games, leaving little doubt that he'd have topped 100 in a full season.

If anything, this big man is getting better at rejecting the opposition in his old age. It's a byproduct of the extra time he's been spending around the painted area, since head coach Gregg Popovich wants to limit the energy he expends on any given night.

Duncan's raw per-game numbers may not match the ones he posted during those MVP campaigns earlier in his career, but he's actually gotten better on a per-minute basis:

After a playoff game against the Los Angeles Clippers in which Duncan recorded a monstrous block on Blake Griffin with less than a minute remaining in the fourth quarter, Popovich told Amick about how his star's timing has allowed him to overcoming his physical abilities:

His timing is just impeccable. He has a hard time jumping over the proverbial piece of paper, and he gets in position. He knows where to be. He's played long enough. He's got a great basketball IQ, and he has excellent timing, so he reads things well. This is really the first time he's guarded Blake was tonight, so for a pretty good portion of the game he guarded him, and he did a great job... That might have been the play of the game when he blocked that shot.

As Amick noted, "Griffin, a five-time All-star, missed 12 of his 15 shots in the second half and was 1-of-9 in the fourth quarter, with Duncan guarding him for much of that time."

At this stage of his career, Duncan doesn't even have to play offense in order to provide value for San Antonio. He's still excellent on that end of the court, but his impact on the point-preventing side is just monumental.

Even during his 18th year in the league, he earned more defensive win shares (4.7) than anyone in the NBA not named Draymond Green or DeAndre Jordan.

The record for someone in their 19th season? Jason Kidd's 2.8 with the New York Knicks in 2012-13.

Duncan's defensive box plus/minus, which indicates how many points per 100 possessions better a league-average team's defense would be with him rather than a league-average defender, was also 4.7 during his age-38 season. Again, that was the No. 3 mark in the league, this time trailing only Rudy Gobert and Andrew Bogut.

The record for someone in their 19th season? Kevin Garnett's 2.8 with the Brooklyn Nets in 2013-14.

Andrew D. Bernstein/Getty Images

No player as old as Duncan has ever been quite so valuable, which is probably what matters most to a team-first player like this big man. As impressive as it may be that he'll likely set the new high-water marks for rebounding and rejections, with an outside shot at doing the same in the scoring column, he's still all about winning.

That's where he ventures into truly uncharted waters. Outside of Abdul-Jabbar, who helped lift the 1988 Lakers to a championship, precious few players this late into their careers have served as key figures on highly competitive squads. And with the exception of his name value, Abdul-Jabbar wasn't truly a star on that title-winning bunch; that role was reserved for players such as Magic Johnson, Byron Scott and James Worthy.

The other veteran who qualifies here is Stockton, though he was putting up big numbers on a Utah Jazz team that won just 47 games and suffered early elimination at the hands of the Sacramento Kings in the first round of the 2003 playoffs.

Though win shares are by no means perfect measures of on-court value, they do provide us with solid summaries of a player's overall contributions. Here, they show us that not many 19th seasons have granted their teams exorbitant levels of value:

Even if Duncan finishes with the No. 2 spot in this category, that's nothing to be ashamed of, especially because he'll be playing for a team that has a serious chance to get through the terrifying gauntlet that is the current Western Conference. The Spurs are unquestionably title contenders, but won't be able to hoist up the Larry O'Brien Trophy without impressive contributions from their longstanding frontcourt star.

He's still that important, even as he nears a 40th birthday that will come at the end of April, when San Antonio is presumably squaring off with one of its first playoff opponents.

Additionally, he does have a shot at toppling Kidd and asserting himself as the win-share leader among this group:

That's just insane.

We've only been comparing Duncan to other players who have spent this much time in the NBA's ranks, but let's step back and just appreciate how long the time frame is here. Fresh off his career with the Demon Deacons, he earned 12.8 win shares as a rookie during the 1997-98 season, and he's on the verge of getting back into double digits nearly two decades later.

Even with all that mileage, he remains one of the best players in the league. That's not even remotely an exaggeration.

In this year's B/R NBA 200 rankings, which were based exclusively on performances during the 2014-15 campaign, Duncan earned the No. 13 spot. His score actually left him tied with both Jimmy Butler and Kevin Durant, though our panel of voters chose to leave him last among that trio.

Rather than looking back, Sports Illustrated's panel looked ahead while ranking the league's top 100 players for the coming 2015-16 campaign. Duncan finished at No. 11. Ben Golliver wrote the following about him, later noting that Duncan had fallen out of the top 10 for the first time since their rankings began in 2013:

The new Netflix series 'Narcos' repeatedly recites an old line, the one about how only the cockroaches will survive a nuclear holocaust. I watched as the show’s camera tracked these perseverant little bugs across a post-apocalyptic desert, and I kept expecting an unfazed Tim Duncan to be banking in jumpers and posting a 20-plus PER somewhere in the dusty background.

Duncan may not be a robot. Although I suppose we do have to leave the possibility open, given his refusal to let Father Time shake him down, there's a strong chance that he's not actually immortal.

Nevertheless, he's on the brink of making history yet again.

The 39-year-old has defied logic and the natural progression of basketball careers for a long time. Now, as he gets ready to kick off his 19th season with the Spurs, he's venturing into more uncharted territory.

No one—not Kareem Abdul-Jabbar, nor John Stockton, nor anyone else has ever been this good for this long.

So much for this sport being a young man's game.

All stats, unless otherwise indicated, come from Basketball-Reference.com.



Adam Fromal covers the NBA for Bleacher Report. Follow him on Twitter:@fromal09.