Cardinals grab lead and put a huge burden on Giants’ Tim Lincecum

ST. LOUIS — For a professional athlete whose shoulders are not particularly broad, Tim Lincecum carries a particularly heavy weight Thursday.

Lincecum carries the hopes of a city and the future of a season.

That would have thrilled the San Francisco Giants three years ago, when he won his second consecutive Cy Young Award, or two years ago, when he won the clinching game of the World Series.

Now the city of San Francisco can only cross its fingers, as the Giants summon the newest and most expensive middle reliever in baseball from their bullpen.

With one swing from an unheralded rookie, the St. Louis Cardinals neutralized San Francisco ace Matt Cain and propelled themselves to a 3-1 victory in Game 3 of the National League Championship Series on Wednesday.

The Giants burned their best pitcher. They sat around in the rain, waiting 31/2 hours, bemoaning all the runners they had left on base. And they lost, falling behind two games to one in the best-of-seven series.

Lose again Thursday, and the series is all but over. For the first time in 18 days, the Giants turn to Lincecum to start.

“He’s the guy we want out there,” San Francisco Manager Bruce Bochy said.

The Giants had the guy they really wanted out there Wednesday. That would be Cain, who has ably filled the Lincecum role as best on staff.

If Cain had won, the worst-case scenario for the Giants would have been the series returning to San Francisco.

But Cain lost, and now the Cardinals can clinch a World Series berth here, if they can beat Lincecum on Thursday and the velocity-deprived Barry Zito in Game 5 on Friday.

“I made a bad pitch,” Cain said, “and it cost us.”

The Giants appeared to have caught a break when Carlos Beltran left the game in the second inning because of a strained left knee.

Beltran is batting .400 this postseason, with three home runs in nine games. The Cardinals replaced him with Carpenter, a rookie who had five at-bats in the division series and struck out three times.

“That’s something you try to take advantage of,” Cain said. “I didn’t.”

In the third inning, in Carpenter’s first at-bat, Cain hung a slider. Carpenter hit a two-run home run, giving the Cardinals all the runs they would need.

Cain controlled the game from there, but the Giants left 11 runners on base over the first seven innings.

After a rain delay of more than three hours, the Cardinals turned to closer Jason Motte for a two-inning save, and the Giants went six up, six down.

So the Giants hold their breath and call on Lincecum, who all but extinguished his star this season. His earned-run average — 5.18 — was the highest in the league, and he was not included in Bochy’s four-man rotation for the division series.

In three postseason relief appearances, he has given up one run in eight innings, with nine strikeouts.

“Maybe he’s figured out something in the bullpen. I don’t know,” shortstop Brandon Crawford said. “But he’s pitched great.”

Said catcher Buster Posey: “He’s pitching with a lot of confidence right now. I think that’s half the battle.”

So, to save their season, the Giants hesitantly tap Lincecum.

“He’s always been a starter,” Posey said. “I think it will feel normal with him starting.”

In a 2010 kind of way, they hope.

bill.shaikin@latimes.com

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