Now Oswalt can only hope that the Phillies can beat Tim Lincecum in Game 5 on Thursday to stay alive. It's up to Philadelphia's other Roy -- Halladay -- to make it happen.
"At this time of year, you just have to pitch," Oswalt said. "It doesn't really matter what the situation is. I thought I had decent stuff."
The Giants' bats said otherwise. Tied, 5-5, since Jayson Werth's double in the top of the eighth inning, all four hitters Oswalt faced made solid contact.
Freddy Sanchez lined out to Werth in right field. Aubrey Huff singled to right on the one pitch Oswalt wanted back -- a first-pitch changeup on the inner half of the plate. Giants rookie Buster Posey followed with a terrific at-bat that ended in a single toward the right-field corner that might have scored Huff had Werth not made a slick sliding stop.
That brought to the plate shortstop Juan Uribe, who missed a second straight start Wednesday because of a wrist injury before entering the game in the top of the ninth. He lifted a 2-2 changeup deep to left field, and Huff scored easily for San Francisco's fourth postseason walk-off win in club history.
As Manuel saw it, Oswalt was the Phillies' best option. The Phils had three available relievers: Right-hander Kyle Kendrick, who has not pitched since Oct. 1 and was not even on the roster in the first round of the postseason; left-hander J.C. Romero, who didn't match well against that right-handed-hitting portion of the Giants' lineup; and closer Brad Lidge, who would have been needed for a save situation had the game reached extra innings. Big league managers almost never use their closer in a tie game on the road, and Manuel followed tradition.
So the game was left to Oswalt.
That didn't surprise Giants manager Bruce Bochy.
"It's that time of year where you see a little different strategy or guys being used," Bochy said. "These are must-win games. No, I saw him warming up. I wasn't surprised at all. He's had some time off. And he's done such a great job for them. They're doing all they can to win the game."
Oswalt has done it before. He made a relief appearance for the Phillies earlier this month as a tuneup for the playoffs, and Wednesday marked his 15th career relief appearance, including two in the postseason.
His other postseason relief stint came for the Astros in Game 7 of the 2004 NLCS, when Oswalt worked two innings in relief of Roger Clemens. Houston lost that game to Woody Williams and the Cardinals, who went on to win the World Series.
"That was a long time ago," Oswalt said.
The more comparable appearance came on July 8, 2006, in Houston, also against the Cardinals. Oswalt had pitched a complete game three days earlier against the Cubs and threw his side session earlier in the day, then iced and prepared to watch the game, just like he did on Wednesday.
When the Astros needed a pitcher in the 10th inning, Oswalt volunteered, and he surrendered a leadoff game-winning home run to Albert Pujols.
"It's a little bit different," Oswalt said. "You don't get to prepare for 30 or 45 minutes before. You just have to go, and you try to make pitches."
Oswalt's teammates appreciated the overtime.
"When I saw him get up, I was confident he was going to go out there and do some things," outfielder Shane Victorino said. "He battled and that's definitely not the position that he's pitching out of. But he tried his best and did his best. Unfortunately, they were able to manufacture that run."
Said Lidge: "That ninth inning is never easy. Throwing out of the bullpen is never easy. But he went down there and volunteered to pitch, and in a game like that, when you're using a lot of relievers, it's nice to have someone volunteer like that. He's done that before. He knows what he's doing. I told him to just do his thing ...
"When you get to the postseason, every game is do or die. We appreciate that Roy went down there, for sure."
Now the Phillies are really in must-win territory. Thirty teams have jumped to a 3-1 lead in the LCS since the best-of-seven format was introduced in 1985, and 26 have advanced to the World Series. The 2010 Giants and Rangers are trying to join that list.
The Phillies, like the Yankees, are trying to survive. All it will take is a three-game winning streak.
"We've won three before," Oswalt said. "We have to come out and swing the bats and pitch good. That's pretty much it. We still have three ballgames to go."
If the series reaches a Game 6, Oswalt promised, "I'll be ready."