Adam LaRoche hit a go-ahead single in a three-run seventh inning, and the Pirates rallied for a 5-4 victory Thursday and a three-game sweep.
The rally started when pinch-hitter Nyjer Morgan bunted down the third-base line and was ruled safe at first by umpire Ron Kulpa for a single. Replays appeared to show Morgan did not beat the throw.
"I had a great view of it and there was no doubt in my mind that he was out," Giants manager Bruce Bochy said. "It's a huge call. Instead of getting the first out there, now they have a rally going."
The Pirates trailed 4-2 against Matt Cain (1-3) when Morgan -- who was optioned to Triple-A after the game -- reached base.
"When we watched the replay, it looked like he was out to us," Cain said.
Jason Bay's double tied the score, Jack Taschner relieved and, one out later, NL RBI leader Xavier Nady was intentionally walked. LaRoche, who hit .174 in April, then lined a single to right just over the outstretched arm of a leaping Eugenio Velez.
"I'm just kind of getting to where I'm confident against left-handers again," said LaRoche, who has a six-game hitting streak but was hitting only .143 against lefties. "It's nice to get in and get a big hit."
Pittsburgh has won 13 of its past 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.
Franquelis Osoria (2-1) pitched a one-hit seventh, and John Grabow and Tyler Yates combined on a one-hit eighth. 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.
"There's been so many games we were coming back in, but we haven't been getting that last hit," Pittsburgh manager John Russell said. "A huge key for us today was that we went ahead and got that extra hit that put us over the top."
Sanchez had three hits and scored twice, and Bay went 3-for-4 with a run and an RBI.
Burriss chopped a single off the glove of Maholm with two on and two outs, and Holm hit a two-run double over center fielder Nate McLouth. Cain, who went 2-for-3, followed with an RBI single up the middle.
Cain gave up five runs and nine hits in 6 1/3 innings.
"He pitched a good ballgame, but there at the end he just made a couple mistakes," Bochy said.
Pirates starter Paul Maholm allowed four runs and six hits in six innings.
"If I don't touch that ball, we're talking about a shutout or a good performance," Maholm said, referring to Burriss' infield hit. "I tried to make the play. It didn't work out, and they had a couple hits after that."
Pittsburgh had lost 13 of 18 entering the series, including three of four in Washington over the weekend.
"We felt like we should have played better in Washington, so to come out here and take three from these guys is a good momentum booster for us," Sanchez said.
- The game was played through steady rain but never delayed.
- Bochy slipped in the wet dugout and hit his head. He could be seen being attended to by training personnel but was fine after the game.
- Giants SS Omar Vizquel, out since spring training after recovery from surgery on his left knee, is close to returning to action. Bochy said the team was hopeful he would return this weekend.