The Giants made a mechanical adjustment to Brandon Belt's swing in May.

He's now playing the best baseball of his brief two-year career.

After providing the game-tying two-run double that sparked a four-run top of the ninth inning in the Giants' victory Friday, Belt was again the offensive catalyst in a 9-8 triumph over Oakland in the middle installment of the three- game Bay Bridge Series on Saturday.

Oakland made things extremely interesting in the ninth, pushing across four, but Clay Hensley induced a game-ending pop up off the bat of Jemile Weeks with the bases loaded, notching his second save of the year.

"It's good to get back and win a series," Giants manager Bruce Bochy said. "These were hard-fought games, both of them could've gone either way."

The 24-year-old Belt capped a four-run sixth frame with a go-ahead two-run homer for the Giants, who recorded their 16th come-from-behind win of the season and second in as many nights. He tallied two hits and three RBI in all, extending his career-long hitting streak to 11 games.

Belt has cracked all four round-trippers this season over his past 11 contests, hitting .441 with three doubles and 12 RBI during the torrid stretch.

Madison Bumgarner (9-4) settled down and hung around long enough to pick up the win. He surrendered four runs on nine hits through his first three frames, but allowed just a pair of hits over his final three innings. He fanned six and walked one.

Tyson Ross (2-7) was charged with five runs -- three earned -- on four hits and four walks in 5 1/3 innings for Oakland, which has dropped two in a row on the heels of an 8-1 stretch.

"When you're down you have to keep grinding and we did," A's manager Bob Melvin said. "It's too bad we didn't win"

The A's held a 4-2 lead after five innings of play, but the Giants used their four-run sixth and a three-run seventh to pull away.

In the sixth, Buster Posey worked a one-out walk and Angel Pagan singled to put runners on first and second. A two-base error by Brandon Moss -- two of his MLB record three errors in the frame -- led to Oakland's demise.

Pablo Sandoval scorched a grounder to first, which bounced off the glove of Moss. He then bobbled the ball as he went to retrieve it near the bullpen, allowing Posey and Pagan to tie the score, while Sandoval reached second.

Belt came up next and smacked a two-run blast to right, giving the Giants a 6-4 edge.

Posey belted a two-run homer in the seventh, while Nate Schierholtz worked a bases-loaded walk to push the margin to 9-4.

Shane Loux began the ninth and gave up three runs on two hits and a walk in two-thirds of an inning. Brandon Inge whacked an RBI single off him before Santiago Casilla took the bump.

Derek Norris ripped a run-scoring base hit and Brandon Hicks' ground-rule two- run double chased Casilla from the game. Javier Lopez came on and walked Seth Smith -- the only batter Lopez faced -- to load the bases for Weeks, who lifted a 2-2 sinker to second for Ryan Theriot, who secured the catch.

Earlier, Josh Reddick smoked a two-run shot to right in the opening inning, but the Giants got both runs back in the second as Sandoval and Belt registered back-to-back RBI singles to knot the contest.

The A's then pushed across a run in the home half and another in the third.

Reddick slapped a run-scoring single to center in the second, while Jonny Gomes stroked a solo blast over the wall in left-center in the third.

Game Notes

Oakland was 4-for-14 with runners in scoring position and left 12 men on base while San Francisco was 2-for-7 with RISP and stranded nine...The A's racked up 15 hits, compared to the Giants' eight.