PHOENIX – A fourth-quarter rally fueled by lay-ups, dunks, and 3-pointers is to be expected in a game featuring the Phoenix Suns. Yet it was the San Antonio Spurs who did it yesterday in the opener of the Western Conference finals.

Tim Duncan, Tony Parker, Brent Barry, and the Spurs proved that defense might be their best thing, but not their only thing. Beating the league’s top offense at their own style, San Antonio used its inside-outside scoring practically to perfection in the final period to beat Phoenix 121-114.

“You got to score points to beat these guys because you are not going to hold them to 82,” San Antonio coach Gregg Popovich said.

Popovich came into this series saying his team’s scoring ability was underrated, yet there was no choice in the first matchup since 1975 featuring the league’s highest-scoring offense (Phoenix’s) against the stingiest defense (San Antonio’s).

The Spurs began making their case by scoring 30 points in the first quarter and 55 by halftime. Then came their amazing closing argument. San Antonio hit 16 of 22 shots in the fourth quarter to erase a seven-point deficit. Their 43 points were the most in any period all season.

“That’s not the kind of quarter that we would expect in a game like this, but we’ll take it,” said Duncan, who soaked his aching left ankle in a whirlpool at halftime and scored 11 of his 28 in the fourth.

With Duncan and Parker working the lane, San Antonio went ahead for good on a jumper by Barry that made it 94-92 early in the fourth. He hit consecutive 3-pointers to make it 106-98 with 4:08 remaining.

Playing 1 1/2 days after closing out Dallas in an overtime thriller on the road, the Suns already had turned an 11-point deficit into an 8-point lead in the third quarter. But they didn’t have another comeback left. The Spurs led by at least six the rest of the way, disappointing the locals who were attending their first conference finals game since 1993.

“We kind of let fatigue affect us mentally,” said Phoenix point guard Steve Nash. “We lost our fight for enough stretches to lose the game.”

Barry scored 13 of his 21 in the fourth quarter. He made 8-of-12 shots, including 5-of-8 on 3-pointers. Parker scored 29 points, Manu Ginobili added 20 points, six rebounds, and five assists, and Bruce Bowen scored just two, but made up for it by holding Shawn Marion to three points.

Nash finished with 13 assists, many setting up Amare Stoudemire’s 41 points. During the season, Stoudemire averaged 38.7 against the Spurs, the most ever by one player.

With the victory, the Spurs claimed home-court advantage, which could be significant since they’re the league’s best at home this season. Game 2 is tomorrow night in Phoenix.

“We’re happy to get this one, but we’re not overly ecstatic,” Duncan said. “We want to get the next one and really hurt them here.”

The Spurs are 3-1 against Phoenix this season, with their only loss coming in a game that Duncan and Ginobili missed with injuries. San Antonio also improved to 34-2 when scoring at least 100; they’re 6-0 this postseason when doing it and 3-2 when they don’t.