The right-hander will seek to lift his potentially weary teammates with another strong outing, and the Giants look to add to Chicago Cubs right-hander Edwin Jackson's struggles while ending a season-worst road skid Wednesday night.
Peavy earned his first win in 19 starts and first in four games for the Giants last Wednesday with a 7-1 victory over the Chicago White Sox. He yielded one run in seven innings after going 0-12 with a 5.25 ERA during his winless drought, which began after an 8-1 victory in Toronto on April 25 pitching for Boston.
The Giants landed the veteran from the Red Sox on July 26, and he went 0-3 with a 4.82 ERA in his first three starts with the club.
"It was just a conversation piece," Peavy told MLB's official website. "Everything has an expiration date."
He now looks to help the Giants regain sole possession of the NL's second wild card spot and trim a 4 1/2-game deficit to the Los Angeles Dodgers in the NL West.
Peavy (1-3, 3.86 ERA) will also try to help the Giants rebound from a rain-shortened 2-0 loss in Tuesday's opener at Wrigley Field, their seventh in 10 games. After playing 4 1/2 innings, the Giants had to wait around 4 1/2 hours before their fifth consecutive road loss was official, their longest skid there since a seven-game losing streak June 15-29, 2013.
Peavy gave up two runs and fanned seven in six innings for Boston in his only other matchup with the Cubs this season, but was saddled with a 2-0 loss June 30. He was tagged for six runs in four innings in his most recent visit to Wrigley - an 8-3 loss for the White Sox on May 30, 2013 - after going 3-2 with a 3.05 ERA in his first seven starts there.
Jackson (6-13, 5.74) didn't fare much better in his most recent start at Wrigley on Thursday, getting charged with five runs in 4 2-3 innings in a 6-2 loss to Milwaukee. He's 0-5 with a 9.10 ERA in his last six home starts and 1-6 with a 6.75 ERA in his last 10 overall.
The right-hander owns MLB's highest ERA among qualifying starters, with John Danks' 4.94 for the White Sox the next closest. His 42 losses since 2012 are also the most of any pitcher.
"At this level, you can't afford to get down," Jackson told MLB's official website. "Obviously, you're disappointed, clearly you don't like the way you pitched. Clearly, I know I'm a way better pitcher than I've been showing.
"You can talk about it all day, but you still have to go on the field and prove it."
Jackson yielded two runs and four hits in 5 1-3 innings in his only other start against San Francisco this season, a 5-0 road loss May 28. He's 1-3 with a 4.75 ERA in his last six matchups.
Former Cub Angel Pagan and Pablo Sandoval have given him the most trouble among current Giants hitters. Pagan is 6 for 9 lifetime against Jackson and Sandoval is 8 for 15.
Chris Coghlan is 3 for 6 in his career versus Peavy and Ryan Sweeney is 3 for 7. Anthony Rizzo, who has four homers in his last eight games, is 1 for 6 with no home runs lifetime against the veteran right-hander.