With Sandoval's status uncertain, Bumgarner tries to help the visiting Giants build on their first victory in a week Tuesday night against the Arizona Diamondbacks.
San Francisco (14-12) snapped its season-high five-game skid with a 6-4 win at Arizona on Monday, but Sandoval left with elbow discomfort. Sandoval, who had two hits with an RBI and is batting .327, was bothered by an elbow injury during spring training but has played in all but one game this season.
With or without him, the Giants should have some momentum.
Brandon Belt homered and delivered a two-out, two-run tiebreaking single in the eighth to help the Giants end a slide that began with two straight home losses to the Diamondbacks (15-11) last week.
"It's been a tough stretch for us here lately,'' said Belt, who is batting .522 (12 for 23) with two homers and seven RBIs in his last seven games versus Arizona. "But I don't think our attitude really changed coming into this game. We knew we had a team that could win and that's what we did.''
The Giants should feel even more confident behind Bumgarner (3-0, 1.87 ERA), who went 5-1 with a 2.31 ERA in his first six starts of 2012 and has yielded seven runs in 33 2-3 innings through five in 2013. He's struck out 34 and walked eight while holding opposing hitters to a .190 average.
Bumgarner gave up one run, five hits and struck out seven in 7 1-3 innings of a 3-2, 10-inning loss to Arizona on Wednesday.
"I felt good," the left-hander told the Giants' official website. "Command felt good and arm felt good. Body felt pretty good. Everything was there."
That's not been the case recently at Arizona for Bumgarner, who is 1-2 with a 5.56 ERA in four starts at Chase Field after he went 1-0 with a 1.26 ERA in his first two there.
Arizona's Martin Prado is 2 for 13 against Bumgarner, but had two hits Monday after suffering through a 1-for-18 slump the previous four contests. Prado, Jason Kubel and Eric Chavez each homered as the Diamondbacks rallied from a 3-0 deficit but lost for the second time in seven games.
"We hit the ball out of the ballpark, we tied it up and they didn't die,'' Arizona manager Kirk Gibson said. "It went down to the end but it just wasn't our night.''
The two-run shot is Kubel's only hit in six at-bats since coming off the disabled list Sunday from a strained quad.
Teammate Trevor Cahill (1-3, 3.00 ERA) takes the ball looking to build on Thursday's performance, when he gave up a run and overcame four walks in five innings of a 3-2 win over Colorado. Though Cahill earned his first win, he hopes to be more efficient after throwing 105 pitches against the Rockies.
"I'm searching for command,'' said Cahill, who has walked 12 in his five starts. "I'm getting behind in the count and it's like I'm losing a feel for the sinker. It's not going where I want the pitch to go.''
The right-hander has walked 12 in seven starts while going 4-2 with a 2.76 ERA versus San Francisco.