It's time for Chauncey Billups to prove his true value.

If the Knicks have any hopes of upending the Celtics in the first round of the NBA playoffs, superstars Amar'e Stoudemire and Carmelo Anthony will need to deliver plenty of scoring, and coach Mike D'Antoni will need to squeeze the most from a rotation that lacks size and length.

But Billups, a 34-year-old point guard with an eternally calm demeanor, will also be a central figure in any upset bid.

The Knicks are loaded with playoff neophytes, and in the Celtics, they face one of the league's most battle-tested teams. But the savvy Billups and his ability to perform in the clutch help balance the disparity in experience.

The Celtics will rely on a trio of future Hall of Famers in Kevin Garnett, Ray Allen and Paul Pierce, but not one of them can match Billups' lengthy postseason resume. He earned the nickname "Mr. Big Shot" when he led the Detroit Pistons to the 2004 NBA title, and he's played in 139 postseason games, 38 more than Allen and Pierce and 43 more than Garnett.

"He's got the mental toughness," Knicks GM Donnie Walsh says of Billups. "And emotionally, he knows how to deal with all of this. And he's obviously done it. It's a big difference when you know you've done it."