SAN ANTONIO – It isn’t Shaq versus Duncan, but the NBA Finals matches the past two champions, an immovable object against … well, another immovable object. The reigning-champion Pistons, who beat the Sixers, Pacers and Heat to get here, were the league’s second-best defensive team. The best defense belonged to the Spurs, the 2003 champs, who toppled the Nuggets, Sonics and Suns. How they match up:

POINT GUARD

Spurs’ Tony Parker vs. Pistons’ Chauncey Billups: Parker is at his best in transition and is effective off high and side pick and rolls, getting in the lane for tantalizing runners. Detroit, which wants to slow him and make him a jump shooter, may post up Billups, who has a clear edge in size and strength, against the speedier, quicker Parker. Billups is a bigshot guy, a terrific pressure free-throw shooter. Edge: Pistons

SHOOTING GUARD

Spurs’ Bruce Bowen vs. Pistons’ Richard Hamilton: Technically, this is Manu Ginobili’s spot, but figure the Spurs put Bowen, their best one-on-one defender, against one of the NBA’s premier twos in a huge matchup for Detroit. Hamilton can get his own shot almost anytime with a couple of dribbles and a pull-up jumper. He’s Reggie-like off the ball, a master using baseline screens. But against Spurs this season, he averaged 9.5 points and shot .308 (8-of-26) in two games. Bowen, a good range shooter, will use a lot of energy defensively. Bowen’s defense is Spurs’ X Factor. Edge: Pistons

SMALL FORWARD

Spurs’ Manu Ginobili vs. Pistons’ Tayshaun Prince: Ginobili is hard to cover. He hits the perimeter jumper, but is just as effective slashing and driving. Prince has been a model of consistency, solid defensively with a huge wingspan. Not a primary offensive option, but he makes shots, especially from the corner. Edge: Spurs

POWER FORWARD

Spurs’ Tim Duncan vs. Pistons’ Rasheed Wallace: Anyone with length or strength gets a shot at Duncan, a dominant player with great back-to-the-basket moves. Not a great passer off the dribble, but an excellent face-up game, good pick-and-pop shooter and superb defender. Wallace is the Pistons’ X Factor. When he plays well, Detroit usually wins. He’s more of a face-up four, but they’ll look to utilize his post-up game. Good rebounder, excellent defender. Duncan is Duncan, but Spurs have not faced a defense like this. Edge: Spurs

CENTER

Spurs’ Nazr Mohammed vs. Pistons’ Ben Wallace: Mohammed has improved his post game, provided decent playoff minutes and played well in spurts. Wallace is an energizer and effort player, especially effective off the ball. Excellent defender. Any offense he provides is gravy. Get by Rasheed, Ben awaits. Get by Ben, Rasheed awaits. Edge: Pistons

BENCH

Spurs’ Robert Horry makes the big shot. Brent Barry is dangerous but inconsistent. Guard Beno Udrih is on the big stage for the first time. Center Rasho Nesterovic played nine minutes against Suns, but his length may be needed here. Detroit has Lindsey Hunter for added defense on Parker. Antonio McDyess gives Pistons an athletic big man who can shoot to 18 feet. Elden Campbell plays when size is needed. Carlos Arroyo goes at point in a pinch. Edge: Spurs

COACHES

Spurs’ Gregg Popovich vs. Pistons’ Larry Brown: Popovich has two rings, Brown one … plus an NCAA crown. Popovich is defense oriented, preaching discipline with great structure. Brown stresses defense, sharing the ball offensively, dribble penetration, offensive rebounds. Edge: Even

PREDICTION: Spurs in 6