SAN FRANCISCO -- The Giants' lead appeared headed down the tubes Monday as a line drive from Kyle Lohse rocketed toward left field.

That was until Giants shortstop Brandon Crawford leapt high to spear the ball, turning a potential two-run single into the third out of the top of the second.

That play, and other defensive gems like it, helped pave the way for the Giants' eventual 9-0 victory over St. Louis to clinch the National League pennant.

"You know, the pitchers are our strength, but we have to catch the ball," Giants manager Bruce Bochy said. "We did such a great job. Crawford was tremendous at short, (Marco) Scutaro. Really, everybody."

How important was the Giants' slick glove work? Just look at how the third inning unraveled for St. Louis in part because of its shoddy defense. The Giants scored five runs, aided by center fielder's Jon Jay's fielding error that allowed a third run to score on Hunter Pence's double.

Later in that inning, Cardinals shortstop Pete Kozma made an ill-advised throw home on Crawford's chopper when his only realistic play was at first.

The Giants shined defensively, and it wasn't just Crawford's highlight-reel catch. Left fielder Gregor Blanco made a running grab of Allen Craig's liner to save a run in the top of the third.

First baseman Brandon Belt made a great stop to his right earlier that inning and threw from his knees to get a force-out at second.

Scutaro shined over the past three games at second base, ranging left to make several nice plays.

"We've played good defense all series, pretty much the entire second half," Crawford said.

But his play to erase Lohse in the second was especially crucial. The Giants went ahead in the first, but with runners on second and third in the next inning, a two-run single off the bat of the opposing pitcher would have been deflating.

"That was a real bad pitch by me," Matt Cain said inside a champagne-soaked clubhouse afterward. "I think that would have really changed the momentum right there, for us to score a run and then give up a run right there. For him to be able to catch that ball kept momentum on our side."

But off the crack of the bat, Crawford wasn't sure what to do.

"It was right over my head," he said. "You could probably tell I didn't know which way to turn. I just had to get up. And the way Cain pitched after that was awesome."

The Giants' five-run third gave them a 7-0 lead, and Blanco said he and his teammates were determined to protect that with good defense.

"We had runs early in the game, but we knew we had to try to keep them off the scoreboard," Blanco said. "They're a great team, and they can do a lot of damage. We knew they could come back."

Follow Joe Stiglich at twitter.com/joestiglich.