That prevented the Cardinals from becoming the first team in the majors to clinch their division and kept the Rockies 3 1/2 games ahead of Atlanta in the NL wild card.
The Giants and Marlins both fell five games behind Colorado in the wild card. Florida lost to the Mets.
After holding Holliday to a 1-for-4 performance in which he stranded five runners, the Rockies sent the meat of their lineup to the plate in the bottom of the ninth.
Torrealba lofted a ball to right, and Ryan Ludwick's throw home was nowhere close.
"When I saw the right fielder kind of backing up that's when I thought, 'OK that's deep enough," Torrealba said after knocking in his 13th run this month after entering September with 14 RBIs.
These teams could meet in the playoffs and the Rockies are 5-0 against the Cardinals this season and have outscored them 35-10.
The one, however, could have gone either way.
"It was a very good game with a fine line," Cardinals manager Tony La Russa said. "They had the last hero."
Huston Street (4-1), one of the players Holliday was traded for last winter, picked up the win with a scoreless ninth.
Holliday, making his first visit to Coors Field as a member of the opposition, slipped out of the clubhouse after the game without comment.
The Rockies, who lead the majors with 59 sacrifice flies, scored both runs that way.
Carlos Gonzalez, another player who came over from Oakland in trade for Holliday, led off the bottom of the first with a double, was bunted over and scored on Helton's deep fly to center off Chris Carpenter.
Carpenter gave up one run and five hits in seven innings, but the only support he received was Ludwick's 21st homer in the seventh off Jose Contreras that tied the game at 1.
Carpenter, a leading candidate for the NL Cy Young award with a 16-4 record, complained that the mound was steeper than the one in the bullpen.
"It was a battle trying to get the ball down," he said.
The best news for the Rockies was that Aaron Cook threw five scoreless innings in his first start since Aug. 21, when shoulder soreness forced him out of a game against San Francisco. He allowed four hits, all singles, got 12 groundball outs and didn't walk a batter in an impressive 76-pitch performance.
"I was stunned as to how sharp he was," Rockies manager Jim Tracy said. "You never know [what to expect] when you have a layoff like that."
Cook said he didn't feel any rust and none showed.
"Cook had a great sinker and had us hitting the ball on the ground. He stayed out of big innings," Ludwick said.
Cook was replaced by Contreras, who hadn't pitched since straining his right thigh while running out a groundball on Sept. 10, in his second start in place of Cook.
The Cardinals had a scare in the eighth when Albert Pujols limped around the first-base bag after hitting a single. He said it was only a cramp: "I feel fine." ... The crowd of 48,847 was the fifth sellout at Coors Field this season.