The 33-year-old right-hander pitched seven solid innings in his fifth start with San Francisco, and the Giants rolled past the Chicago Cubs 8-3 on Wednesday, hours after they won a protest regarding a rain-shortened loss from the night before.
Peavy (2-3) has won two straight after losing his first three starts with San Francisco following a July 26 trade from Boston where he was 1-9.
"I never gave up hope or thought I wasn't going to win," Peavy said. "I didn't really do anything different tonight other than just the team scored and made my job a whole lot easier.
"We've got five or six more starts and I've got to try to find a way to win those with us trying to get in (the playoffs)."
Peavy allowed 10 hits, struck out eight and walked none. Chris Valaika's two-run homer in the second inning accounted for the only runs against him.
The Cubs' Luis Valbuena added a solo homer and a triple in going 3 for 4.
Struggling starter Edwin Jackson (6-14) was hit hard in just 2 2/3 innings, his shortest outing of the season. He allowed seven runs, eight hits and two walks. Jackson has lost seven of eight decisions.
"It's just terrible," Jackson said. "There's no excuse for it, pretty much. Tonight I didn't help myself. I didn't help my team."
Before the game, the Giants won their protest filed with Major League Baseball over Tuesday night's rain-shortened loss that was called in the fifth inning.
A problem in getting the tarp onto the field caused unplayable conditions, and the game was ruled a 2-0 Cubs win after a delay of over four hours. The suspended game will be completed on Thursday before the regularly scheduled game between the teams.
"We needed Jake to get somewhat deep in the game," manager Bruce Bochy said. "A long day tomorrow. We have a lot of innings to play."
MLB ruled the tarp hadn't been properly put away after its previous use, and therefore there was a "malfunction of a mechanical field device under control of the home club."
MLB said this was the first successful protest since 1986.
On Wednesday, the Giants jumped out to a 4-0 lead in the first inning as five of their first six batters reached base. Ishikawa drove in two runs with his first double to cap the outburst.
Ishikawa doubled in another run in the third and scored on Susac's first career homer as San Francisco opened a 7-2 lead.
Pence led off the fourth against Carlos Villenueva with his 17th homer of this season to make it 8-2.
The suspended game will resume on Thursday with the Cubs batting in the bottom of the 5th inning and leading 2-0. San Francisco's Yesmeiro Petit (3-3, 3.89) and Chicago's Jacob Turner (4-7, 5.80) will step in to start that one. In the regularly scheduled game, Giants LHP Madison Bumgarner (13-9, 3.14) is slated to face Cubs LHP Travis Wood (7-10, 4.86).
Giants: C Buster Posey was out of the lineup because of soreness in his left hip. Bochy likened it to an unscheduled day off and expected Posey to be back behind the plate on Thursday.
Posey is batting .278 with 13 home runs. He was replaced by Susac.
Cubs: SS Starlin Castro was a last-minute scratch from the lineup due to a family emergency. The team didn't provide details or say how long he would be out, but said it was likely he'd be placed on the bereavement list.
LHP Felix Doubront, placed on the DL with a left calf strain on Aug. 1, threw on the side on Wednesday. He is expected to make another rehab start at Double-A Tennessee on Sunday or Monday. Manager Rick Renteria said Doubront, acquired from Boston on July 30, is in line to be recalled and start on Aug. 30 when the Cubs play a doubleheader at St. Louis.
The infield was still damp and the areas under the stands at century-old Wrigley Field reeked of mold even more than usual following Tuesday's night's downpour that led to the game being called at 1:16 a.m. The storm apparently was very localized. Cubs GM Jed Hoyer said it didn't rain at his house, some 12 blocks from the ballpark.