Nine postseason games have drawn a single lineup from Cardinals manager Mike Matheny, who has derived success through consistency.

A man of multiple positions and relatively little major-league experience, rookie Matt Carpenter watched, waited and understood.

A team’s need to improvise found him Wednesday afternoon at Busch Stadium.

A game that may ultimately define the National League championship series twisted in different directions before bending to the home club. A first-inning misstep by right fielder Carlos Beltran thrust a third-inning opportunity at Carpenter, who responded with a two-strike, two-out, two-run lightning strike that largely explained a 3-1 Game 3 decision over the San Francisco Giants.

The Cardinals invested far more than Carpenter’s telling at-bat against Giants starter Matt Cain. However, the improbability of a bench player’s sixth postseason at-bat added to the vibe surrounding a team finding ways to win.

"Tonight was one of those things that you can’t expect but you can still be ready for. And I think I was," Carpenter said.

Now leading the series 2-1, the Cardinals won a game Wednesday they have lost numerous times this year. The Giants finished with more hits but were punished for stranding 11 runners while going 0 for seven with men in scoring position. The Cardinals got two runs from Carpenter’s one swing, then added on when Giants second baseman Marco Scutaro couldn’t make a clean play on a bases-loaded grounder in the seventh inning.

"Guys did a great job every inning putting pressure on them. But we were missing a big one tonight," Giants manager Bruce Bochy said.

Cain pitched more efficiently than Cardinals starter Kyle Lohse, who termed his 52/3 innings as "grind-y" before giving way to a four-man tag team that covered the final 10 outs. The Giants created 12 baserunners against him, advancing six into scoring position.

Five days after he worked two innings in the NLDS clincher over the Washington Nationals, closer Jason Motte gained the first two-inning save of his career when a rain delay of more than three hours drove set-up man Mitchell Boggs from the game after the seventh inning.

"If these guys come in here today and beat us today it’s two in a row," Motte said. "It’s one of those things you get the win today, you’ve got two more at home, and you try to do everything you can to take both of them."

The Cardinals are unsure how long Beltran may be sidelined by what the club described a strained left knee. They are certain they lead the National League championship series because of Carpenter’s pick-me-up.

Without a start since Oct. 3, Carpenter turned around a fifth-pitch slider he saw from Cain for a 421-foot home run to transform the Cardinals’ early 1-0 deficit into a 2-1 lead. The hit was Carpenter’s second of the postseason and was not dissimilar from his success as a pinch hitter this season.

Cain is "one of the best in the game, obviously," Carpenter said. "I think we all know that. Every at-bat I’ve had against him has been really tough. They’re always a battle."

And Carpenter won each of the first five. Carpenter entered Wednesday four for four in his career against Cain, which elicited a pregame question to Matheny about whether he considered starting him.

Finding playing time for Carpenter became one of Matheny’s most challenging tasks this season — so much so that Carpenter made the first two starts of his professional career at second base. He spread 67 starts among five positions when not contributing 11 pinch hit RBIs. He hit .294 and fit 46 RBIs within 296 at-bats.

"You play 162 games and you see a little bit of everything," Carpenter said. "I’ve come in the bottom of the first. I’ve come in the top of the second. Things like this that happen throughout the year get you ready for something like this. Obviously, tonight was a bigger stage but it’s something I’ve done before."

"People will talk about the sample size, but to me Carpenter is a guy we try to get at-bats for whenever we can," Matheny said. "He’s earned that through the season. Skip Schumaker is the same way. We’re not afraid to use these guys, even though we haven’t used them much."

Bothered by knee and hand problems for much of the second half, Beltran enjoyed renewed vigor in his final four regular-season appearances. He spoke of feeling "level" after contributing a home run in Sunday’s series opener. He reached base five times during the team’s extended Game 5 comeback against the Nats. But that progress may have unraveled when Beltran extended for the first-base bag while trying to outrun a first-inning double play.

Matheny’s predecessor, Tony La Russa, cultivated a reputation for aggressively putting his hands on the postseason canvas. Matheny has resembled the anti-TLR by using the same lineup and the same batting order in each of his team’s nine playoff games. Beltran’s condition may push him off that tendency tonight.

The Cardinals lead the series despite batting only .198. Their postseason average stands at .238. They have 13 hits the last two games, and cleanup hitter Allen Craig remains hitless for the series.

The Giants, meanwhile, have deeper issues.

Bochy confirmed after the game that struggling Game 1 starter Madison Bumgarner will not pitch Friday’s Game 5. Lefthander Barry Zito will.

Bochy may also reconsider right fielder Hunter Pence’s place in the lineup after Pence became a foil in several Cardinals escapes Wednesday.

With the Giants leading 1-0 in the third inning with one out and runners at first and third, Lohse induced a 6-4-3 double play from Pence.

"I threw the best slider I could," Lohse said. "I missed with two. In that situation you’ve got to go with what got you in that count. If I miss with a fastball down 2-0 (in the count), it’s one of those things you can’t let happen."

After escaping a fourth-inning jam on center fielder Angel Pagan’s fly ball, Lohse used another double play to erase Scutaro’s leadoff single before he walked MVP candidate Buster Posey. Pence grounded out.

Pence returned in the seventh inning to find more frustration against the Cardinals’ bullpen. With the tying run on second base, Pence struck out against Boggs, who also got first baseman Brandon Belt to end the inning. The Giants stranded 11 before the eighth inning.

Matheny aggressively worked the game ways other than lineup. He double-switched Craig from the seventh inning and pulled Trevor Rosenthal after the righthander retired one hitter to end the sixth inning.

Edward Mujica started the seventh inning in keeping with the Cardinals’ bullpen formula. One-out turbulence forced Boggs into the game. Rain arrived after Boggs struck out the two hitters he faced to end the seventh.

"There are always hard calls. You have faith in people to get outs," Matheny explained. "I was really trying not to let the rain dictate the moves we made. You never know when the pivotal point of the game is going to be."

Motte was approached about 30 minutes before the game resumed regarding a two-inning save. He shrugged his acceptance, set about preparing and later retired all six hitters faced.

"If you’re in position to win, you try to win right now," said Matheny, who had resisted double-switching Craig from Game 1 of the Nationals series under a similar circumstance.

"Any time you’re in the lead late in a game you do what you can to hold on to it," Lohse said. "We did."