He's already established himself as one of the all-time greats. The notion that he has something left to achieve looms largely because he's still trying to achieve. Had he retired after coming up empty last season, few would have thought any less of what he's done for the San Antonio Spurs.
All the same, titles carry historical significance. They transcend our preoccupation with numbers and production, speaking to an ability to actually win at the highest level.
The metrics for evaluating greatness at that level are varied and debatable. By any of those metrics, Michael Jordan remains in a class of his own. He won, put up gaudy numbers and was dominant over an extended time frame.
The more open question is who signifies the generation after MJ.
The conventional response is Kobe Bryant, winner of five titles and one of the greatest all-around scorers ever to touch a basketball. And we know that LeBron James is the man right now and for the foreseeable future.
However, there's a strong argument to be made that Duncan is really the bridge between MJ and LeBron—that, even more than Kobe, Duncan has risen to the top of his generation. The mere insinuation will smack of heresy to most Los Angeles Lakers fans.
But fans of the game itself should keep an open mind. Duncan is better than you think, which is really saying something given that most of us already have a pretty high opinion of him.
Duncan's career regular-season numbers are impressive enough. He's averaged 19.9 points, 11.1 rebounds and 2.2 blocks per game since coming into the league.
As is well-documented by now, the Wake Forest product had his most productive seasons before Tony Parker and Manu Ginobili emerged as primary scoring options.
He was the league MVP in 2002 and 2003, the first time averaging 25.5 points, 12.7 rebounds, 3.7 assists and 2.5 blocks per game.
That gives you some idea of what Duncan was capable of doing at his best, and it helps put the rest of his career in perspective. Had the NBA remained a big man's league and the Spurs not shifted their system in the mid-2000s, the career numbers would be even more impressive.
They might not measure up to Bryant's when it comes to scoring alone, but scoring alone is a pretty myopic means of assessing a player this well-rounded.
So are regular-season numbers.
That's where the playoff career comes into focus.
Duncan ranks third all-time in career rebounds during the postseason behind Bill Russell and Wilt Chamberlain. Since blocks weren't recorded in their days, Duncan leads the league in that category—well ahead of Kareem Abdul-Jabbar and Hakeem Olajuwon.
According to Basketball-Reference.com, Duncan is seventh all-time in postseason player efficiency rating at 24.69. Kobe ranks 23rd on that list.
Even though scoring is a just a snapshot of Duncan's game, he ranks fifth all-time in postseason points, where he predictably trails Bryant—who's in third place behind MJ and Kareem.
In the final analysis, Bryant has been more productive—especially on the offensive end. However, Duncan's efficiency and defensive numbers are certainly good enough to keep him in the discussion.
It doesn't hurt that he's always passed the ball well for a big man. He's even improved his free-throw stroke in recent years.
If you really let all the numbers sink in, it becomes increasingly harder to deny that Duncan's the best of his time. Even then, numbers really don't tell the whole story.
Some will argue that no one is more competitive than Bryant. They mistake Duncan's demeanor for something it's not. Let's not forget just how eager Duncan told reporters he is to face those same Miami Heat again.
We also shouldn't forget that Duncan spends all offseason keeping himself in amazing shape so that he can continue winning at a high level.
Leadership comes in different shapes and sizes. Duncan's brand has been truly unique. He's neither especially vocal nor too shy to make a point. The generally even-keeled big man is demonstrative when he has to be, delivering admonitions to his teammates on an as-needed basis while letting his play do most of the talking.
The big story surrounding Duncan has long been his willingness to defer. As the league changed and moved away from post offense, so too did the Spurs.
Duncan didn't complain.
He readily allowed Parker and Ginobili to adopt more prominent scoring roles, taking the reins as San Antonio integrated a more high-octane motion offense.
Lesser stars would have clamored for touches. They would have complained about the club's philosophy at the first sign of adversity. They would have put their own interests before the team's interests.
Not Duncan. That's not his style.
There's really not much use in comparing leadership styles. Kobe's is different—we know that much. But Kobe and Duncan have had different teams with which to work, different coaches guiding them, different obstacles in their ways.
It's not so much that Duncan's been a better leader than Bryant. It's just that he's done things that Bryant probably would have scoffed at doing.
He's taken a backseat when he was still more than capable of scoring 20-plus points per game. He's rejected the spotlight, evaded the fame.
Successful as Bryant's Lakers have been—especially when dominant bigs like Shaq were around—Duncan's willingness to eschew the big numbers and larger-than-life persona have been uniquely key to keeping the Spurs at a certain level of success year in and year out.
Taking that step back has given others an opportunity to shine, establishing a model for team basketball that many try to replicate with only varying degrees of success.
As SI.com's Chris Mannix put it in 2010, "Duncan's status among the all-time great big men is a topic of frequent debate. Is he between Hakeem and Moses? What about Shaq and Bill Walton? But it's irrelevant, really. Duncan's greatness is not in his ability to win individual battles. It's in his ability to elevate a team."
He's been elevating the Spurs in a way few could have imagined since 1997.
And that speaks to something else that sets him apart.
If Duncan claims his fifth title, he will have won at least one in three different decades.
Just let that sink in for a moment.
The first came way back in 1999, when David Robinson was still at his side. Duncan was still learning at that point, growing into the player who'd soon inherit San Antonio and build a new foundation.
Countless role players have come and gone. Avery Johnson, Steve Kerr, Robert Horry. Despite the revolving door of new faces, the Spurs have always been really, really good. Even during their "off" years, they've been better than most.
San Antonio has advanced to the postseason in every single year that Duncan's been in the NBA. During that span, it's lost in the first round just three times. Duncan's Spurs have won the Southwest Division a remarkable 11 times and never finished worse than second in the division.
This season was the ninth time during the Duncan era that San Antonio advanced to the conference finals and the sixth time it will compete in the NBA Finals.
The debate shouldn't be about whether that constitutes a dynasty. It should be about whether it sets new expectations for what a dynasty should look like. Duncan didn't win his titles and move on to the next stop, chasing rings wherever the best opportunity lay.
He remained in San Antonio and did whatever it took to ensure the titles came to him. And he's still doing it.
The scary thing is that he could probably help these Spurs contend for another two or three years—at least if he wanted to. While there's no denying that Kobe's continued to do amazing things late into his career, his teams haven't been as consistently successful—even when accounting for injury.
The brief stretch between Shaq and Pau Gasol was a disaster, and the Lakers would have struggled for the last two seasons even with a healthy Bryant.
The Spurs have never taken that kind of downturn under Duncan.
Winning is all he knows. It's all he'll ever know.