The road ahead for Dirk Nowitzki

In every athlete's life, there is a moment that determines what they are all about. It isn't just their legacy at stake in this moment, nor is it how they'll be viewed. It's more than that. It's the moment that defines them, and most athletes who reach that superstar, one-of-the-greatest-of-his/her-generation's level see that moment coming and embrace it.

And because of that embrace, they fail. They don't get what they wanted out of the moment. They don't get what their careers need.

So those moments are not to be embraced; they are to be seized. Those who don't seize them when they arrive regret it for the rest of their careers, and often for the rest of their lives.

Dirk Nowitzki had that moment in 2006, and embraced it. Dwyane Wade, on the other hand, seized it at the same time. And for five seasons now, Nowitzki has been waiting, wondering whether the moment will ever come again for him. One disappointing and uninspired playoff appearance after another began to take a toll. Not on him, necessarily, but certainly on his legacy. And finally, after five years of living in what used to be called Peyton's Place (which is where the Indianapolis Colts' Peyton Manning seemed to reside until he finally won a Super Bowl, a place that creates questions about whether a superstar has the heart to win a title), the moment has returned for Nowitzki.

The question is: Has he finally learned how to seize it?

The experts -- from Charles Barkley on TNT to Chris Broussard on ESPN's "First Take" -- are saying that Nowitzki, without question, has been the best player in these playoffs. He's been playing at a level that makes it impossible to argue or disagree. Stephen A. Smith went so far as to say that Dirk, at this moment, is "the best white player since Larry Bird."

But the glaring difference between Nowitzki and Bird is staring him in the face right now. It isn't just that Bird has three rings to Nowitzki's zero; it's Bird's ability to put a choke hold on a series and make another team wilt under the impact of his play.

The Dallas Mavericks have sneaked up on everyone in the past few weeks. Their dismantling and dethroning of the Lakers will be talked about for years. Nowitzki versus Pau Gasol was Hakeem Olajuwon versus David Robinson circa the 1995 Western Conference finals. But unless Dirk has it in him to take the Mavs to another level, and then another level, everything he has done thus far to put himself back in front of this moment -- where he can erase the stigma that is a large part of his past -- will mean nothing.

Essentially, Nowitzki has more pressure on him to win a ring right now than LeBron James does. A claim that applies to no other player on the four teams left alive.

Not trying to overstate or overexaggerate, but the Mavericks-Thunder Western Conference finals -- which begin Tuesday night in Dallas (ESPN, 9 p.m. ET) -- are the official beginning of how the rest of Nowitzki's career will unfurl. It isn't "Now or never." It's "Now or … Oh well, you are who we thought you were."

Which, right now, is this: A player who at times was the best in the game but who didn't have the (fill in the blank) to will postseason victories. A player who could average 28 points a game in the conference finals, as he did against Phoenix in 2006, but couldn't seize both twice-in-a-lifetime moments when they came. In the NBA Finals against Wade and Miami five years ago, Dirk averaged 22.8 points, and the Mavs lost in six games.

Because, although stats and facts don't lie, they rarely tell the whole story. And Nowitzki's moment right now, beginning with this series against the Thunder, is all about what he can do to prove that the already-finished chapters of his career aren't the whole story.

Some will read this column and say that for Dirk's career, it's not that serious. They'll say he doesn't need to prove anything more than he already has. They'll claim that regardless of what happens in this series or the next, regardless of those outcomes, Nowitzki will go down as one of the greatest players we will ever see play this game.

But I'll say what many of us know to be true for him at this moment: "That is simply not enough."

Scoop Jackson is a columnist for ESPN.com.