San Francisco ? Roy Halladay rarely sat down between innings, riding a bicycle to keep loose after pulling his groin. He gutted it out on the mound, sending the Philadelphia Phillies home with a chance for their third straight National League pennant.

Philadelphia’s Carlos Ruiz, left, celebrates with Raul Ibanez after both scored in the third inning of Game 5 of the NLCS. The Phillies won, 4-2, Thursday in San Francisco.

Most of his teammates didn’t even realize their ace was pitching in pain. Doc got the best of The Freak this time in a rematch of aces — and on one bad leg.

“The guy’s just a tough guy,” Placido Polanco said. “He didn’t show it.”

Halladay outdueled Tim Lincecum and kept the Phillies alive with a 4-2 victory over the San Francisco Giants on Thursday night that pulled Philadelphia within 3-2 in the NL championship series.

“It was just something to deal with. You make adjustments and pitch your way through it,” Halladay said of his injured right groin. “We know we can win. It’s a matter of going out and doing it. We continue to plug away.”

Having spoiled the Giants’ clinching party, the Phillies headed home on a redeye charter, hoping to stage a celebration of their own this weekend.

Jayson Werth’s solo homer in the ninth quieted the raucous sellout crowd of 43,713, and many fans began making for the exits even before the final out.

Some of Halladay’s teammates had noticed he wasn’t at his best.

“There was a sense of that something wasn’t entirely right,” Werth said. “But when we went back out there — I mean, guys get dinged up all the time and stay in the game and have things going on. So the fact that he went back out there kind of told me that it wasn’t that severe. But at the same time looking up at his velocity I knew that he wasn’t throwing as hard.”

Halladay’s bunt — which appeared to be foul — also helped spark a three-run third inning, when Shane Victorino drove in the first of two runs that scored on a fielding error by first baseman Aubrey Huff.

Victorino’s hard grounder hit off the bottom of Huff’s glove and wound up in shallow center field as two runs scored. Polanco followed with an RBI single that made it 3-1.

Philadelphia forced a Game 6 back home in Citizens Bank Park on Saturday and another cross-country trip. Jonathan Sanchez starts for the Giants against Roy Oswalt, who is 10-0 in 12 starts in Philly this year. Oswalt was the loser in relief in Game 4.

“Obviously, we play good at our ballpark in front of our fans, and kind of regained home-field advantage a little bit,” said Werth, whose 13 career postseason homers are tied for the most by NL players.

Halladay improved to 2-1 with a 2.45 ERA in three postseason starts this year, doing it despite the injury, sustained in the second inning.

“Of course, he stayed in there,” Phillies manager Charlie Manuel said. “He was determined he was going to stay in there.”

Philadelphia took his matchup of Cy Young Award winners after Lincecum came out on top in the opener. The Giants now must win once in two tries on the road for the franchise’s fourth pennant since moving West in 1958. San Francisco has not been to the World Series since the Giants’ Barry Bonds-led team lost Game 7 to the Angels in 2002.

After Ryan Madson struck out the Giants’ 4-5-6 hitters in the eighth, Brad Lidge finished with a perfect ninth for his second save this postseason.

Philadelphia will try to become the 12th team to rally from a 3-1 deficit in a best-of-seven series. The Red Sox were the last to do it, in the 2007 ALCS against Cleveland.

“From our perspective, we see ourselves more in the driver’s seat than them,” Lincecum said.

San Francisco put the possible tying run in scoring position in the fourth, fifth and sixth innings but couldn’t capitalize, losing in a potential postseason clincher at home for the first time since Game 7 of the 1962 World Series against the New York Yankees.