PITTSBURGH -- Adam LaRoche hit a go-ahead single in a three-run seventh inning, and the Pittsburgh Pirates rallied to beat the San Francisco Giants 5-4 Thursday for a three-game sweep.

Pittsburgh has won 13 of its last 15 games against San Francisco and swept three-game series from the Giants in three straight seasons, according to the Elias Sports Bureau. San Francisco has lost four in a row overall.

The Pirates trailed 4-2 against Matt Cain (1-3) when pinch-hitter Nyjer Morgan reached on a bunt single starting the seventh. Sanchez, 7-for-13 after being moved to the leadoff slot for the first time this week, followed with a ground-rule double and Nate McLouth hit sacrifice fly.

Jason Bay's double tied the score, Jack Taschner relieved and, one out later, NL RBIs leader Xavier Nady was intentionally walked. LaRoche then lined a single to right.

Franquelis Osoria (2-1) pitched a one-hit seventh, John Grabow and Tyler Yates combined on a one-hit eighth and Matt Capps finished for his eighth save in as many chances, striking out pinch-hitter John Bowker with a runner on second to end the game.

Sanchez had three hits and scored twice, and Bay went 3-for-4 with a run and an RBI.

Pirates starter Paul Maholm allowed four runs and six hits in six innings, while Cain gave up five runs and nine hits in 6 1-3 innings.

Ryan Doumit hit a two-run single in the third, but San Francisco took a 4-2 lead in the fourth when Emmanuel Burriss and Steve Holm had consecutive hits that drove in their first major league RBIs.

Burriss chopped a single off the glove of Maholm with two on and two outs, and Holm hit a two-run double over centerfielder Nate McLouth. Cain followed with an RBI single up the middle.