The surprising Pirates, seeking their first winning season since 1992, are 40-35 and second in the NL central.
Burnett (9-2) allowed three runs and six hits, striking out seven. The winning streak is his longest, and it's the first time a Pirates pitcher has won eight in a row since Dock Ellis in 1974. Michael McKenry caught Burnett for the first time because starter Rod Barajas is injured. "I was really impressed with McKenry," Burnett said. "He was outstanding. I can't say enough about him. It was a pleasure to work with him. He picked up where Rod left off."
Eric Kratz and Pence hit homers for the Phillies.
The Pirates jumped on Kyle Kendrick (2-8) for five runs before he recorded a second out in the first. "Gave us a chance to win, pitched deep into the game, which they needed me to," Kendrick said. "We came up short."
Drew Sutton led off with an infield single and Neil Walker walked. One out later, Garrett Jones hit an RBI single. McGehee followed with a three-run shot to left and Alvarez then lined one out to right to make it 5-0. McGehee has five homers and 15 RBIs in June after driving in just six runs with no homers in the first two months. "I think at one point I was trying to do too much," McGehee said. "I was with a new team trying to make a good impression. Then I went back to just trying to hit the ball up the middle of the field."
Kratz connected off Burnett in the second to cut it to 5-2. Burnett retired nine straight before consecutive singles by Shane Victorino and Pence put runners on first and third with one out in the sixth. Placido Polanco's fielder's choice grounder scored Victorino to cut it to 5-3. Pence led off the bottom of the eighth with a shot off Jason Grilli for his 14th home run of the season and first since June 2, snapping a 98 at-bat homerless drought.
Grilli pitched out of a jam with two runners on to preserve the lead. He struck out pinch-hitter Jim Thome and retired pinch-hitter Carlos Ruiz on a foul pop. First baseman McGehee made a nice running catch and held onto the ball after stumbling into the first row down the right-field line.
"We got some tough outs from Grilli and Joel," Pirates manager Clint Hurdle said.
Kendrick settled down nicely after the awful start. He gave up five runs and six hits in seven innings.
This was Burnett's first appearance in Philadelphia since losing to Cliff Lee and the Phillies in Game Five of the 2009 World Series. Burnett beat Pedro Martinez in Game Two that year and the New York Yankees prevented the Phillies from repeating as world champions by taking the Series in six games.
The Phillies finished 5-5 on their longest homestand of the season. The five-time defending NL East champions fell back into last place and are 36-42, including 17-24 at home.
NOTES: Phillies designated RHP Chad Qualls for assignment and called up RHP Brian Sanches and LHP Jeremy Horst... 1B Ryan Howard started a rehab stint at Class-A Lakewood on Thursday night. The 2006 NL MVP hasn't played for the Phillies this season after tearing his left Achilles' tendon last October... Lee (0-4, 3.72) tries again for his first win when the Phillies open a three-game series in Miami on Friday night.