ATLANTA -- Brooks Conrad hasn't lost his knack for delivering in the clutch as a pinch-hitter.
Conrad, who had three homers -- including two grand slams -- and drove in 12 runs as a pinch-hitter last season, singled home Alex Gonzalez from second base.
Gonzalez, who had a two-run homer in the fifth, opened the ninth with a pop fly off Ryan Franklin (0-3) that bounced off shortstop Ryan Theriot's glove for an error. Gonzalez moved to second on Joe Mather's sacrifice before Franklin walked Nate McLouth.
Conrad hit a fastball from Franklin into shallow center field to drive in Gonzalez.
He was mobbed by teammates near first base after the game-winning hit.
"It's the best feeling," Conrad said. "Anytime you can get a base hit like that, it feels really good. Walk-off hits like that are few."
Injuries to Martin Prado and Chipper Jones forced Conrad into the starting lineup at second base late last season, but he committed four errors in the first three games of the Braves' NL division series loss to San Francisco.
The Braves stuck with Conrad as a utility infielder this year, and he provided a reward against the Cardinals.
X-rays at the stadium showed the broken bone. The Cardinals did not say how long Freese is expected to be out.
"It's a bone on top of another bone type of deal," Freese said, adding he will see a doctor in St. Louis on Monday. "I'll see what they say. Maybe I'll need surgery just to speed up the process."
Jonny Venters (1-0) pitched a perfect ninth.
Derek Lowe gave up six hits and four runs in five innings three days after his DUI arrest.
Lowe was charged with DUI, reckless driving and improper lane change on Thursday night after he was spotted by a Georgia State Patrol trooper racing another car down an Atlanta street.
Lowe wouldn't answer questions about the DUI after the game. He abruptly ended an interview session when asked a third question about the arrest.
Lowe was shaky in the first inning, giving up three runs on four hits.
"It just wasn't a good start," Lowe said. "We found a way to keep it close."
The Cardinals, who had comebacks to win the first two games of the series, couldn't hold a 4-0 lead. Matt Holliday had a two-run double in the first. Lance Berkman and Albert Pujols added run-scoring singles.
Atlanta's Dan Uggla knocked Jaime Garcia out of the game in the seventh with a drive off the top of the center-field wall. Uggla thought he hit a homer, but the umpires ruled the hit was a double. They confirmed the ruling with a quick video review.
Gonzalez followed with a grounder to first that Pujols mishandled for an error, allowing Uggla to score for a 4-4 tie. Prado's single off Jason Motte drove in Mather to give Atlanta the 5-4 lead.
Garcia gave up five hits and four runs in six-plus innings.
Lowe settled down with three strong innings before the Cardinals pushed the lead to 4-0 in the fifth when Pujols drove in Garcia with a single up the middle.
After Garcia threw four perfect innings to open the game, the Braves broke through in the fifth when Brian McCann singled and scored on the homer by Gonzalez. Mather walked, moved to third on McLouth's broken-bat single and scored on pinch-hitter Brandon Hicks' single to left.
The Cardinals couldn't score after loading the bases against Linebrink with no outs in the sixth. Berkman, who led off the inning with a single, was thrown out at the plate on Theriot's grounder to third baseman Chipper Jones. Brian McCann threw to first to complete the double play, and George Sherrill struck out Garcia to end the inning.
Pujols moved from first base to third base in the eighth. It was his first appearance at third base since Sept. 23, 2002 against Arizona. Mark Hamilton entered the game at first base in a double-switch as manager Tony La Russa brought right-hander Franklin in to pitch.
Hicks' pinch-hit single was his first major league hit. ... Punto left the game in the fourth inning due to tightness in his left hamstring. Daniel Descalso replaced Punto at second base. ... The attendance was 34,129, including 559 dogs for Bark at the Park day.