Burrell lined Peavy’s 96 mph full-count fastball into the left-field stands as Philadelphia won for the fourth time in six games.
“Fortunately, I got just enough of it,” Burrell said.
Lieber (11-10) held the Padres to two runs and six hits in six innings before three relievers shut down the Padres in the final three innings. Lieber struck out four and had one intentional walk.
“Lieber stayed out there and gutted it out,” Phillies manager Charlie Manuel. “I thought about the fourth and fifth he was getting into a little trouble, but he wiggled out of it.”
The Phillies pulled within five games of the NL East-leading Atlanta Braves, who lost 8-0 to Arizona. It is the closest Philadelphia has been to the lead since July 26.
After enduring a 31-pitch first inning, Peavy (10-5) settled down to shut out the Phillies the rest of the way on three hits. Overall, Peavy allowed three runs and five hits in seven innings.
But the one fastball to Burrell stuck with Peavy.
“It was just a bad pitch,” Peavy said. “I just didn’t do what I needed to do there and, unfortunately, it cost us the game.”
Peavy stuck out nine to set a single-season career high with his 174th strikeout and took over the major league lead.
“He’s got good stuff,” Burrell said. “We were fortunate to get some early runs. Usually three runs is not enough to win a game.”
“That whole lineup is tough on me,” Lieber said. “My location has been much better lately and I pitched down in the zone.”
“The count is full there and I’m looking for a fastball that I can do something with,” Burrell said. “I got one I could handle there and it worked out well.”
Peavy received defensive help in the seventh when Giles made a diving catch in short right field on Jimmy Rollins’ fly ball with runners on first and second and two outs.
Peavy, who pitched a five-hitter in a 3-0 win at Washington in his last start, had allowed just four runs over last three starts, spanning 24 innings.
Philadelphia appeared to catch a break in the bottom of the seventh when pinch-runner Damian Jackson got tagged out after rounding too far around second base. After pinch-hitter Robert Fick singled with one out, he was replaced by Jackson. Dave Roberts followed with a hard hit-and-run single to center.
Jackson ran hard around second base and pulled up after Lofton threw to second baseman Chase Utley. Although television replays appeared to show that Utley miss Jackson with a swipe tag, Padres manager Bruce Bochy said umpire Jim Wolf told him he called Jackson out for running out of the basepath when he tried to avoid the tag.
“I don’t know how you can be out of the baseline when you reach a base in the same move,” Bochy said. “The call and timing was horrible and I didn’t agree with it.”
After a heated argument, Wolf ejected Bochy from the game.
Lieber is 9-4 lifetime against the Padres in 20 games, including 18 starts. Lieber has walked two batters in his last 30 innings against San Diego. … Peavy allowed more than two earned runs for the 15th time in 50 starts dating back to the start of the 2004 season. … Burrell, 28, hit his 150th homer to become the eighth-youngest Phillies player to reach the mark.