Philadelphia ? The ultimate ace, it turned out, belonged to the St. Louis Cardinals.

Chris Carpenter tossed a three-hitter to outpitch old pal Roy Halladay in a duel for the ages and St. Louis edged the Philadelphia Phillies, 1-0, Friday night in the deciding Game 5 of their NL playoff series.

The wild-card Cardinals scored in the first inning when Rafael Furcal led off with a triple and Skip Schumaker followed with a double.

And that was it.

Heavily favored Philadelphia, which featured four accomplished aces in baseball’s best rotation, never broke through against Carpenter. Ryan Howard grounded out to end the game and hurt his leg coming out of the batter’s box — he limped a couple of steps and crumpled to the ground as St. Louis started to celebrate.

“It was some kind of fun,” Carpenter said.

“He’s a great friend of mine, and like I said, he did a great job tonight also,” he said.

The Cardinals needed a monumental collapse by Atlanta in the final month and major help from the 102-win Phillies just to reach the playoffs. Now they’re heading to Milwaukee for the NL championship series starting Sunday following a stunning upset in which they beat three of Philadelphia’s four aces: Halladay, Cliff Lee and Roy Oswalt.

“Actually, I don’t know what to say,” Phillies manager Charlie Manuel said. “I just got through talking to our team, and basically when I look at it, we played 162 games, and definitely we had the best record in baseball.”

“I know that we’re capable of going farther in the playoffs. Our goal was to get to the World Series. It’s been that way for two years now,” he said.

Three of the majors’ four opening-round matchups went to a deciding Game 5, and all of them were pitching-rich thrillers. Detroit held off the New York Yankees, 3-2, on Thursday night, and Milwaukee beat Arizona in 10 innings earlier Friday.

Then, the showdown between Carpenter and Halladay topped them all.

“Roy Halladay is, at this time, probably the best pitcher in the game and we were able to go out and jump ahead, which was huge,” Carpenter said.

Trailing two games to one, the Cardinals began their comeback with a win in Game 4. That night in St. Louis, a squirrel scampered across home plate as Schumaker batted in the middle innings — if the Cardinals keep winning, their fans will certainly go nuts, thanks to their “Rally Squirrel.”

Coincidentally, a squirrel was caught at Citizens Bank Park before Game 5. Not a good omen, apparently, for the Phillies.

“I think guys we’re just relaxed and having fun,” Carpenter said. “We put ourselves into position where everybody was expecting us to have no chance and we just started playing like the team we knew we were. And we were fortunate to get some help back into it with Atlanta losing and we were playing well the rest of that month.”

Carpenter was over 100 pitches when he took the mound in the ninth. He retired Chase Utley on a fly to the warning track in center and got Hunter Pence on a grounder.

Howard was next, and Carpenter got the big slugger to end an improbable series win.

St. Louis trailed the Braves by 101/2 games on Aug. 25, but went 23-8 the rest of the way and earned a wild-card berth after Game 162 when Philadelphia completed a three-game sweep in Atlanta.