San Francisco, CA -- (Sports Network) - Lance Berkman's solo homer in the ninth inning provided the winning run, as Houston overcame a six-run deficit to top San Francisco, 8-7, in the finale of a four-game set with the Giants.

Berkman finished 2-for-4 with three runs batted in, and remained red-hot. He has hit safely in 13 consecutive games, and has posted a .556 batting average with seven homers and 20 RBI in the span.

Kaz Matsui went 3-for-4 with a double, while Carlos Lee finished 3-for-5 with a solo homer and Darin Erstad provided a pinch-hit, three-run homer for the Astros, who took three of four games from the Giants, and have won 11 of 13.

Starter Chris Sampson allowed seven runs -- five earned -- on 10 hits in six innings, but the Astros' bullpen threw three scoreless innings. Tim Byrdak (2-0) threw two-thirds of an inning for the win.

Omar Vizquel and Randy Winn each had three hits, while John Bowker drove in three runs for San Francisco, which has lost eight of 11.

Giants starter Tim Lincecum was solid in six innings, as he allowed three runs on five hits and three walks, and struck out 10. But Tyler Walker, who turned 32 on Thursday, allowed four runs in two-thirds of an inning out of the bullpen, while Vinnie Chulk (0-2) gave up Berkman's homer and took the loss.

The Astros had been down by as many as six, and trailed the Giants by four entering the eighth inning. Lee hit a solo shot to right to get one back. Geoff Blum then struck out on a wild pitch, and reached base, and Mark Loretta followed with a single.

Erstad was inserted as a pinch-hitter, and lofted the second pitch into the seats in right field to tie the game at 7-7.

"It was a poorly executed pitch to Lee, a fastball right down the middle. Erstad, I went ball one. I didn't get ahead and ended up throwing it right down the middle," Walker said. "Basically you can blame me for losing this game...There were six outs to go with a four-run lead. I know the Astros are a good-hitting team, but that's our job."

Berkman completed Houston's comeback in the ninth inning, which he led off. Chulk had been inserted in the eighth and ended the Astros' rally then, but his first-pitch changeup was hammered by Berkman over the right-field seats and splashed into the bay for an 8-7 Houston lead.

"Those are mistakes I just can't make. I thought it was too bad a pitch to take a swing at but it stayed right there and floated right over," Chulk said.

Jose Valverde worked a scoreless bottom of the ninth for his 11th save of the season.

"Any time you lose a game like this they are tough. You are really in command, five outs away with a four-run lead. Those are tough to lose," Giants manager Bruce Bochy said.

The Giants edged in front in the bottom of the first, when an error by the shortstop Loretta allowed Vizquel to race home from third. Then, a sacrifice fly from Bowker brought in Winn for a 2-0 San Francisco lead.

The home team continued to add runs in the third. Fred Lewis and Vizquel led off with singles, and Winn punched a double that bounced off the wall in left and drove in one run.

Aaron Rowand then grounded a single through the left side to plate Vizquel and leave runners on the corners. A Bowker double cleared the bases, and pushed the Giants' lead to 6-0.

But the Astros set out on their comeback in the next frame, which Matsui led off with a single. Hunter Pence followed with a double to put both in scoring position, and Berkman knocked them in with a single to right.

Berkman later advanced to third on a ground out, and Loretta's RBI single made it a 6-3 game.

Another error by Loretta allowed Vizquel to score in the home half of the fourth, and push the Giants' lead back to four.

Game Notes

On Thursday, the Giants placed pitcher Merkin Valdez on the 15-day disabled list retroactive to May 13, and purchased the contract of pitcher Alex Hinshaw from Triple-A Fresno. To make room on the 40-man roster, they transferred infielder Kevin Frandsen to the 60-day DL...Winn extended his hitting streak to 10 games...Astros reliever Geoff Geary left the game with a strained groin...Byrdak has not allowed a run in 11 appearances (9 1/3 innings) this season...It was Erstad's first career pinch-hit homer.