SAN DIEGO -- Wil Nieves lined a fourth-inning grand slam off Giants right-hander Jake Peavy and the Padres held on Sunday for a 6-4 victory, San Diego's third in its four-game series against the reigning World Series champions.
Peavy made his first Petco Park appearance since the Padres traded him to the White Sox at the 2009 Trade Deadline. He finished the fourth inning and left the game after Nieves' homer erased San Francisco's 2-0 lead.
"I thought he was pretty sharp," Giants catcher Buster Posey said of Peavy. "He looked probably as crisp as I've seen him the last three or four times I caught him. He really didn't make too many mistakes."
Referring to the 1-1 pitch that Nieves crushed, Posey added, "Unfortunately, there was the one that came back and stayed over the middle and he made us pay for it."
Padres starter Tyson Ross, who has won his last three decisions against the Giants, surrendered three runs and five hits in six innings.
"It was a good team win," Ross said. "It's a grind and I didn't have my best stuff today, but I'm going to give it everything I've got. The guys picked me up today."
Will Venable hit a seventh-inning homer for the Padres, offsetting Posey's homer in San Francisco's half of the inning.
MOMENTS THAT MATTERED Memorable reunion: Nieves and Peavy have some history, as the two were batterymates for the Padres in Nieves' Major League debut in 2002. The 37-year-old Nieves got the better of the reunion by hitting his first career grand slam. More >
Missed opportunities: The Giants left five runners in scoring position, twice squandering chances with a runner on third base and one out. In the seventh inning, Nori Aoki was doubled off first base on Joe Panik's popup immediately before Posey homered. More >
Amarista pads the lead: After San Francisco pulled within a run on Gregor Blanco's RBI triple in the sixth, Alexi Amarista answered with one of his own in the bottom of the frame, sending a ball down the line in left field that kicked past Aoki and scored Justin Upton for a 5-3 advantage.
Dealing with forced hand: Because Casey McGehee was unavailable for the Giants due to the cortisone shot he received for his bruised left leg, manager Bruce Bochy had to let reliever Yusmeiro Petit bat in the sixth inning with Blanco on third base and two out. Petit struck out.
"There were a lot of fist pumps, a lot of smiles. Guys jumped. That was good stuff. The grand slam is a special play in our game. You don't see it every day." -- Padres manager Bud Black on Nieves' grand slam
WHAT'S NEXT Giants: Bochy hopes the hoisting of the 2014 World Series banner preceding Monday's 1:35 p.m. PT start vs. the Rockies will remind his players that they remain capable of dynamic, winning efforts. Somebody needs to make sure to get that message to Chris Heston, the first rookie to start a Giants home opener since Alan Fowlkes in 1982.
Padres: San Diego opens a three-game set at 7:10 p.m. on Monday against another National League West opponent, the Arizona Diamondbacks. Andrew Cashner will look to improve upon his last outing in which he served up three home runs to Dodgers first baseman Adrian Gonzalez and took the loss after allowing six runs.
Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. Tim Powers is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.