Philadelphia’s Cliff Lee reacts after striking out the final batter of the game. Lee pitched a six-hitter, and the Phillies defeated Colorado, 5-1, on Wednesday in Philadelphia.

Philadelphia ? One strike away from a shutout, Cliff Lee stepped off the mound, took a deep breath and allowed himself to enjoy the moment.

Quite a debut for a postseason rookie.

Lee dominated the Colorado Rockies, tossing a six-hitter, and the Philadelphia Phillies began their World Series title defense with a 5-1 victory in their playoff opener Wednesday.

Raul Ibanez had two hits and two RBIs, and Ryan Howard and Jayson Werth drove in runs with key extra-base hits off 15-game winner Ubaldo Jimenez.

Lee, the reigning AL Cy Young Award winner, struck out five and had no walks in his first career playoff start. He retired 16 straight batters at one point until Garrett Atkins hit a wind-blown double in the seventh. Lee lost his shutout when Troy Tulowitzki doubled in a run with two outs in the ninth.

“I had him 0-2 and I stepped off and wanted to give myself a chance to absorb it all,” Lee said. “Then I threw three straight balls and allowed a double in the gap. Maybe it cost me a run. Whatever, we had a five-run lead.”

Game 2 of the best-of-five NL division series is set for today with Cole Hamels, last year’s World Series and NLCS MVP, on the mound for the Phillies against Colorado’s Aaron Cook.

Some questioned manager Charlie Manuel’s decision to give Lee the ball over the playoff-tested Hamels for the first game. But Lee made his manager look brilliant with a masterful performance.

On a day when swirling winds made flyballs difficult to track, Lee ignored the elements and shut down the NL’s second-highest scoring offense. Avoiding the adventures that come with the Phillies bullpen, Lee mixed a deceptive fastball with off-speed pitches, had pinpoint accuracy and threw 113 pitches.

“He was aggressive, he had good tempo and rhythm and he handled the whole flow of the game real good,” Manuel said.

The hard-throwing Jimenez was equally impressive against the league’s No. 1-scoring offense for four innings, but ran out of gas in the fifth. He got chased with no outs in the sixth after allowing nine hits and five runs in five-plus innings.

“Up until the fifth, it was one of the better games he had pitched over the course of the month,” Rockies manager Jim Tracy said. “He was really, really on his game into the fifth. He had all his stuff.”

A sellout crowd of 46,452 — the largest in the six-year history of Citizens Bank Park — rocked the ballpark, waving their white-and-red “Fightin’ Phils” towels. The Phillies were 7-0 at home last October and set a franchise attendance record this season.

Werth, one of five All-Stars in Philadelphia’s lineup, got it started with a walk in the fifth. He scored when Ibanez ripped a double into the right-field corner.