Spurs forward Tim Duncan, owner of four NBA titles himself, knows this look well.

"It's definitely different being the defending champion," Duncan said. "People come in every night, and you've got a target on your back. It doesn't matter who it is or what team you're playing, they're always going to bring their best against you."

Especially if that team happens to be the previous NBA champion.

The Spurs, the league's 2007 title-winner, resume their rodeo road trip today with a high-noon showdown against the newly crowned Celtics.

It is a red-letter date the Spurs have had circled on their calendar in Celtic green for some time now, ever since Kevin Garnett, Paul Pierce, Ray Allen and Co. officially supplanted them as king of the NBA hill last June.

"It's going to be a great game, a great challenge," Spurs guard Tony Parker said. "We're going to be very motivated, and they're going to be very motivated."

As if the Spurs needed more in the motivation department.

Much of the Basketball-playing world already seems to have ordained an NBA Finals rematch between the Celtics and Lakers. No matter that the Spurs are still very much in the conversation among the league's elite.

At 33-15, they are in second place in the Western Conference behind the Lakers, and head into today's game holding a 31/2-game lead over New Orleans in the league's toughest division.

Spurs coach Gregg Popovich says he seldom uses his team's "under-the-radar" status to inspire his players. He wouldn't be surprised, however, if they use it to inspire themselves.

"It probably does bug them, because they're human beings," Popovich said. "It never materializes into somebody saying, 'We never get respect.' But they play for that."

The Spurs can forget about getting the Rodney Dangerfield treatment in Boston. The Celtics, who at 42-10 trail only Cleveland in the Eastern Conference, have had this game earmarked as well.

"Everybody talks about the Lakers," Boston coach Doc Rivers said. "I'm amazed people keep forgetting about the Spurs. They're just a fundamentally sound, great Basketball team."

Boston center Kendrick Perkins went a step further, intimating he was relieved it was the Lakers, and not the Spurs, who came out of the Western Conference last season.

"I think if they had made it, it would have been a tougher (NBA) Finals," Perkins said.

From afar, the Spurs recognize the formula the Celtics used to hang their 17th championship banner last summer. It is much the same formula the Spurs used to hang four since 1999.

The Celtics surrounded their three stars with productive role players - 3-point gunner Eddie House, grappling big man Glen "Big Baby" Davis, the since-departed James Posey and since-inactive Sam Cassell - and leaned hard on an attack-dog defense.

Led by Garnett, the league's reigning defensive player of the year, the Celtics' defensive dominance hasn't waned. Boston ranks first in the league in field-goal percentage defense (42.5) and second in scoring defense, allowing just 92.3 points a game.

Popovich is quick to label the Celtics "the best defensive team we'll face all year."

"They focus on defense, no question," said Spurs guard Roger Mason Jr., who faced Boston four times with Washington last season. "That's the anchor of their team. That's the reason they won the championship last year."

The Spurs will witness the fruits of that labor this afternoon.

Indeed, the Celtics have another banner in the rafters, but they won't be the only team in the gym with a target on their backs.

"You can't ever count the Spurs out," Perkins said. "They're going to come with it. They're a championship team."