PITTSBURGH -- At the end of his memorable day, second baseman Neil Walker was much more interested in talking about his double-play partner.
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"He's one of the best teammates I've ever had," Walker said. "He's helped me a lot and he has helped this team a lot by playing great defense. It was good to see him come up with the big hit."
Walker homered and doubled as the Pirates overcame an early 5-0 deficit and ended San Diego's six-game winning streak. The Padres had won 11 in a row at Pittsburgh dating to 2009.
Andrew McCutchen and Michael McKenry each drove in two runs during the big inning against Ross Ohlendrorf (4-3) and Cory Burns. Barmes, a 10-year veteran, has 88 career home runs.
"It was the biggest home run of my career," Barmes said. "I've never hit a grand slam before and it came in a big situation when we needed something big to happen. If felt good, really good. I was excited."
Walker had the third five-hit game of his career and second this season, the other coming July 8 against San Francisco.
However, Walker was much happier for Barmes, who has struggled offensively all season after signing a $10.5-million, two-year contract in the offseason as a free agent. He is hitting just .217 after going 2 for 5.
Barmes hadn't committed an error in 34 straight games until making two in the first four innings before redeeming himself with the grand slam.
Pittsburgh stopped a three-game skid. On Friday night, San Diego rallied from six runs down for a 9-8 victory over the Pirates.
"Clint's swing was his biggest of the season and it might have been the biggest of the season for us," Hurdle said. "We kind of felt we got slapped by our girlfriend in front of our mother [on Friday] and we just needed something to feel good about."
The Pirates sent 14 batters to the plate in the fourth inning. McKenry drew a bases-loaded walk from Ohlendorf just before Barmes' slam and then singled in the final run of the inning.
"They ambushed us there in the fourth inning and we just couldn't make the pitches along the way to stem the tide," San Diego manager Bud Black said. "If you've been around the game long enough, you'll run into those innings where everything they do works, everything you do doesn't and you can't stop the momentum. You've just got to take it."
McCutchen, who leads the major leagues with a .362 batting average, ended a string of 11 hitless at-bats with a double in the fourth. He finished 2 for 6.
The Pirates remained 4 1-2 games behind Cincinnati in the NL Central and moved 2 1/2 games in front of St. Louis for the second wild-card spot.
"We're capable of having games like this," Walker said. "From one through eight in the lineup, we can all hit."
Erik Bedard (7-12) made it through five shaky innings for the win, allowing five runs -- three earned -- and five hits with four walks and six strikeouts. The left-hander improved to 5-0 in his career against the Padres.
Pitching in Pittsburgh for the first time since being released last October after going 13-27 in four seasons with the Pirates, Ohlendorf was tagged for seven runs -- six earned -- on five hits in three-plus inning while walking three and striking out one.
Logan Forsythe and Jesus Guzman had two hits each for the Padres and Chris Denorfia led off the game with his fourth home run.
Denorfia's homer started a four-run inning. Guzman hit an RBI single and two more runs scored when Barmes, the shortstop, made a throwing error on a groundball by Cameron Maybin.
Forsythe doubled with one in the second and scored when Chase Headley hit a tapper up the line that McKenry, the catcher, fielded and threw to the first for the out. Forsythe raced home when no one covered home plate.
Walker hit an RBI single in the second to pull the Pirates to 5-1 then moved in front 10-5 with the big fourth inning. The nine-run inning was Pittsburgh's biggest since it also scored nine on July 20, 2010, against Milwaukee.
Walker homered off Brad Boxberger to lead off the seventh.
San Diego signed 1B-OF Mark Kotsay to a one-year contract before the game that carries through the 2013 season. The 36 year old is hitting .275 with one home run and nine RBI in 55 games. ... Pittsburgh activated RHP Juan Cruz from the 15-day disabled list and optioned RHP Jared Hughes to Triple-A Indianapolis. Cruz missed 23 games because of shoulder inflammation.. Pirates RF Travis Snider did not start because of tightness in his right hamstring but pinch hit in the sixth inning and walked. ... The 113,539 series attendance was the second-highest for a three-game series in PNC Park's 12 seasons. ... The Padres open a four-game series at Atlanta on Monday night with LHP Eric Stults (2-2, 2.72) facing Braves LHP Mike Minor (6-8, 4.95). The Pirates begin a four-game home series with the Dodgers on Monday night with RHP Jeff Karstens (4-2, 3.77) pitching against Los Angeles RHP Aaron Harang (7-7, 3.80).