Once upon a time, Tim Duncan played as much as any NBA superstar.

In Duncan's rookie year of 1997-98, he averaged more than 39 minutes per game, good for seventh in the league. A year later, he did much the same thing, in the lockout-shortened season. By 2001-02, he topped 40 minutes per game, good for the second-most minutes in the league, and still topped 39 per contest in 2002-03.

But a funny thing happened to Duncan's minutes as he entered his late-20s, hardly the time of any player's decline. They dropped to 36.6 in 2003-04, to 33.4 in 2004-05, and they haven't topped 35 since.

And over the past five seasons, Duncan's minutes per game is just under 30. His Player Efficiency Rating, for a period generally associated with decline, is 23.3, which is both excellent and not far from his overall career PER of 24.7.

And Spurs coach Gregg Popovich, responsible for Duncan's minutes throughout his career, believes this has prolonged and improved Duncan's career.

"I do think that him playing the way he is at this late date has something to do with the way we've handled him," Popovich said in an interview prior to the Spurs' 103-89 loss to the Nets, a game they played without Duncan, Manu Ginobili, Tony Parker, and several other key players.

Interestingly, despite the Spurs' success with Duncan, other teams haven't followed suit with their superstars. Take a look at the PER leaderboard in 2013-14: Kevin Durant is at 38 minutes per game, LeBron above 37, Kevin Love and Anthony Davis in the 36 range. Poor Carmelo Anthony is at nearly 39 per game.

Then again, Woodson is on the hot seat, perpetually, in a Knicks organization that has endless turnover. And as Popovich pointed out, that means that not all coaches have the same kind of mission from higher up to think long-term.

"Whether other people do it or not, I think, is pretty individual," Popovich said. "Circumstances are different on every team. Some people are under different pressures. Sometimes that gets into the equation, too. You just can't do it. I don't really worry too much if anybody else does what we do."

But there's a middle ground between the Spurs and the Knicks, consisting of, essentially, the 28 other franchises. And even on the continuum more closely aligned to the San Antonio end, things haven't changed much, in terms of usage patterns.

"It's basically -- I mean, he's obviously going to play the majority of the minutes," Thunder coach Scott Brooks told me about Durant last week. Brooks is an example of a long-tenured coach, and works for Sam Presti, a forward-thinking GM who came from, that's right, the Spurs, where he pushed for San Antonio to draft Tony Parker. "Some might think I'm not very smart, but I'm pretty smart in that area. I'm gonna play Kevin Durant a lot of minutes. But I try to keep it right around 39 to 40. There's some games he can play more. That's the thing. Kevin's a really good player."

So right now, it's really just the Spurs doing this. The only player in the top 25 in PER with fewer than 30 minutes per game is Duncan. And the only other player in the top 25 in PER with fewer than 32 minutes per game is... Parker.

Expand to the top 30, and the only player with fewer than 25 minutes per game is... Ginobili.

To hear Popovich tell it, this has more to do with individual circumstances than any larger motivation. I asked him whether any particular piece of information led his Spurs to making this revolutionary change, one that is far more unusual than his more-publicized efforts to give Duncan, and others, occasional days off.

"Analytical information, that everybody deals with? Do I look analytical to you?", Popovich said, smiling.

Turning more serious, he continued: "No, it's just our circumstances... we've always, since the beginning, been more concerned with [Duncan's] longevity, protecting him, since we knew what we had.

"And Manu, I think I could make the argument that he's got more minutes on him than any player in the NBA, including Kobe, when you think about what he's done every summer since, I don't know how many years in a row, practicing twice a day, all summer, playing in the games, that kind of thing. So I thought it was important for those guys to make sure they were taken care of.

"And Tony, I thought as time went on, he was gonna have to carry us a bit. So I didn't want to run him into the ground. So it just took on a sort of mantra with us, to keep them at a certain level."

Anyone who's been present for a coaching press conference before and after a game can only marvel at this kind of long-range planning. So often, NBA coaches will stress a need to limit a player's minutes, only to admit, after the game, they needed to rely on their player more.

But the "mantra", as Popovich put it, has meant the Spurs are careful with their aging veterans in Ginobili and Duncan, careful with their mid-career star in Parker. And don't forget the impressive 22-year-old, Kawhi Leonard. He's averaging 28.6 minutes per game, too.

This is not to say Popovich is unwilling to stretch his guys occasionally. Nor is he willing to acknowledge any calm about losing a random regular season game in February, even though this strategy inherently includes the risk of sacrificing such games. I tried to get him to acknowledge this during his postgame media availability. It didn't go well.

But even on the rare occasions when Popovich does stretch his players, however, he makes certain to figure out how he's going to make it up to them, to keep the long-term minute toll at a comfortable level, and a lower average mark than the key players on every other NBA team.

"We have a ballpark figure that we want them to average for the season," Popovich said prior to the game, in a more accommodating mood. "And that's always in my mind. So, if in recent history, if Timmy's played, you know, 32-to-34 minutes per game, that's too much, so I'll want to make sure I limit myself in the next 4-5-6 games to make sure he's 26-to-28 minutes, or something like that.

"So it's always there, but based on what happens. Like last night, it was 44, obviously. Someone has to do a little work, to get that down, statistically. Fortunately, one game won't skew it that much."

And accordingly, Duncan sat Thursday night. The average of 44 and zero, of course, is 22.

So the Spurs roll on. They lost to the Nets, but their 36-14 record this year is still good for second-best in the Western Conference. They finished two games behind the Thunder last year, but ultimately made it to the NBA Finals. The Thunder played Durant 81 games, at 38.5 minutes per game, and Russell Westbrook around 35, and for all 82 games. Durant shot 5-for-21 in a Game 5 loss to the Grizzlies. Westbrook hurt his knee in the playoffs.

There's no proof that playing fewer minutes could make the difference for the Thunder, or the other 28 NBA teams. But that team with all the championships, defending its Western Conference title from last year, sure seems to think it works.

"For Timmy tonight, this is his third game in four nights," Popovich said Thursday. "You play him, what, 44 last night? I'd be an idiot to play him tonight."