SAN FRANCISCO (AP) — Jesse Chavez exhausted himself trying to work out of a long first inning. The Athletics' starting pitcher wasn't around much after that.

One day after Oakland used four relievers after the team traded pitcher Scott Kazmir to the Houston Astros in exchange for a pair of minor leaguers, manager Bob Melvin was forced to go deep into his bullpen for a second straight game.

Chavez allowed four runs and eight hits in a season-low three innings in the A's 9-3 loss to the San Francisco Giants on Friday night.

"They made him work pretty hard," Melvin said after Chavez threw 80 pitches in his short night of work.

"He was just missing with early count stuff where he was getting behind, and then they fouled off a bunch of pitches," he said. "They made him work. Sometimes you have to give the hitters credit. They had a good approach tonight."

Hunter Pence had four hits and drove in two runs, Brandon Belt had three RBIs and Jake Peavy (2-4) pitched six strong innings to earn his second straight victory for San Francisco. Buster Posey extended his hitting streak to 10 games with three hits and drove in a run, and Joe Panik and Angel Pagan each also drove in runs for the Giants, who won their ninth in 10 games.

Ben Zobrist homered for the A's, who lost their third in four games. Eric Sogard and Billy Burns, who left the game early with an injury, also drove in runs.

Not much else went right for Oakland, which still seemed to be in a daze following the Kazmir trade.

Chavez (5-10) was especially off after throwing six scoreless innings in his previous outing. Chavez walked two, struck out one and labored after throwing 34 pitches in the first inning.

"All night they did it to every one of us that went out there," Chavez said. They didn't give in, they didn't chase down, they didn't expand the zone. You have to tip your hat to them on that point."

Burns is doubtful to play Saturday after suffering a testicular contusion. He left after the third inning after fouling off a ball during his at-bat in the top of the inning. He took several minutes to gather himself following the incident and finished the at-bat. He recorded an RBI groundout.

Peavy allowed three runs and five hits in just his sixth start of the year. The former Cy Young Award winner missed two months with a back strain and hip discomfort. Peavy did not walk a batter and struck out two.

Sogard's single against Giants reliever George Kontos scored Billy Butler in the seventh. It marked the first inherited runner to score against Kontos this season. He stranded 26 runners before the hit.

TRAINER'S ROOM:

Athletics: Switch-pitcher Pat Venditte threw exclusively from the right side during his one-inning rehab appearance with the Single-A Stockton Ports on Thursday and will throw exclusively from the left side on Saturday. ... LHP Sean Doolittle (left shoulder strain) will throw on flat ground Saturday and will likely throw a bullpen at the end of the month. ... RHP Taylor Thompson (right shoulder strain) allowed four runs in two-thirds of an inning for the Ports and pitches again Sunday. ... OF Coco Crisp (cervical strain) is expected to begin a rehab assignment soon. "We're mapping something out," Melvin said.

ANGEL IN THE BULLPEN:

The A's recalled RHP Angel Castro from Triple-A Nashville and optioned RHP Arnold Leon to Nashville before the game. Castro makes his second tour this year. He was 0-1 with a 3.00 ERA in four games in May. Leon was recalled Thursday for his fourth stint with Oakland and tossed 3 1/3 innings against Toronto.

UP NEXT:

Athletics: RHP Chris Bassitt (0-2, 2.93) will be recalled from Triple-A Nashville to start Saturday. He has made three starts for the A's, the last on July 11. "It's a chance for him to get settled in," Melvin said. "He's done all he can and it looks like he'll be here for a while."

Giants: LHP Madison Bumgarner (10-5, 3.27) makes his fourth career start against the A's, his first at home. He's 1-2 with a 6.41 ERA against them.