Scutaro left after the fifth because of his damaged left hip. X-rays were negative, and he'll likely get an MRI on Tuesday. There was no word on his future status.
"You're trying to get to the second baseman and obviously try to knock him down so he can't turn a double play," Holliday said. "As long as you're in the baseline, it's within the rules."
The series now shifts to St. Louis for three games, starting with Game 3 on Wednesday when San Francisco ace Matt Cain takes on Kyle Lohse of the Cardinals.
Things got off to a testy start when Holliday barreled into Scutaro at second base to break up a potential double play in the first inning. The play riled up a crowd that had seen three straight losses by the Giants so far this postseason.
There was plenty to cheer all night for the Giants. Ryan Vogelsong pitched seven strong innings, Angel Pagan hit a leadoff homer to give San Francisco its first home lead this postseason, and Scutaro broke the game open with his single off Chris Carpenter.
Making Scutaro's hit even sweeter for the Giants was the fact that Holliday misplayed the ball in left field, allowing a third run to score on the error.
The Giants also benefited from a missed call by an umpire in the eighth inning after St. Louis center fielder Jon Jay made a spectacular, diving catch to rob Brandon Crawford of a hit.
Jay threw toward first and the Cardinals should have gotten a double play, but first base umpire Bill Miller did not see Allen Craig tag Gregor Blanco's jersey as he raced back to first on the play.
St. Louis manager Mike Matheny argued the call and the umpires huddled to discuss it, but they kept the safe call even though replays showed Craig made the tag. The Giants capitalized when Ryan Theriot hit a two-run single to make it 7-1.
Back at Busch Stadium, Holliday will be cheered after being the target of boos all night following his aggressive play on the basepaths.
With runners on first and second and one out, Craig hit a bouncer to Crawford, and the shortstop quickly flipped to Scutaro for the forceout.
Holliday, a former high school football star in Oklahoma, came tumbling in and slid late into Scutaro, crushing his left leg to prevent up the double play. Scutaro lay on the ground twisting in pain while trainer Dave Groeschner and Bochy ran out of the dugout to attend to the second baseman.
"As I watched it live it looked like it was a hard slide," Matheny said. "It didn't go out of the baseline to get him. Once again, I haven't looked at it again, but we teach our guys to go hard. Play the game clean, play it hard, not try and hurt anybody."
"I hated to see that it ended up that way. That's not how we play the game. But we do go hard, but within the rules," he said.
Vogelsong got out of the jam by retiring Yadier Molina on a groundout and Scutaro stayed in the game with a limp until being replaced in the sixth by Theriot.
By then, he had done his damage with the bat in the big fourth inning.
The rally started innocently enough with a bloop, opposite field double by Brandon Belt and a chopper over third baseman David Freese by Blanco. Crawford then hit a bouncer between the mound and first base that Carpenter fielded and threw away toward first base. It appeared Crawford may have impeded Carpenter by running inside the baseline but the Cardinals did not argue the play.
With the bases loaded and two outs, Scutaro lined his single to left-center that Holliday misplayed to the delight of Giants fans, putting Carpenter and the Cardinals into a 5-1 hole.
Vogelsong made the lead hold up by becoming the first Giants starter to make it through six innings this postseason. He allowed four hits and one run for his first career postseason win.
"It was unbelievable. It was fun to watch," Pagan said. "It was very tough tonight. All his pitches were right in the zone, you know, hitting the corners and getting the hitters off balance. That was the key for him tonight."
These teams have a history of contentious meetings in the NLCS from Jeffrey Leonard's one-flap down home run trot in 1987 that riled up the Cardinals to a benches-clearing dustup 10 years ago when St. Louis reliever Mike Crudale buzzed Kenny Lofton after he showboated on a home run.
San Francisco answered with the bats this time as Pagan led off the bottom of the first with a homer matching his feat from Game 4 of the division series against Cincinnati. The Giants had been outscored 20-6 and never led in two home losses to the Reds and the Game 1 defeat to the Cardinals.
The Cardinals tied it in the second inning when Pete Kozma drew a two-out walk and scored on Carpenter's RBI double, his third hit already this postseason.
But Carpenter, making his fifth appearance in 2012 after complicated surgery to remove a rib and two neck muscles, wasn't nearly as sharp on the mound or in the field. He allowed five runs two earned and six hits in four innings, failing to add to his 10 career postseason wins.
"He's been real sharp lately," Matheny said. "Today they just got a few things going. We couldn't get it stopped until there were too many runs on the board. We have faith in him in these situations and know he'll come out next opportunity and make good pitches for us." Game notes
Philadelphia's Jimmy Rollins is the only other player with two leadoff homers in a single postseason, doing it in 2008.
Cardinals OF Carlos Beltran reached base three times, doubling twice and walking once.
Giants 3B coach Tim Flannery performed the national anthem with the Grateful Dead's Bob Weir and Phil Lesh.
Vogelsong doubled in the sixth to become the first Giants pitcher to get a postseason extra-base hit since Jack Bentley homered in the 1924 World Series.