"I think I have a better chance of going out and doing what I'm capable of doing," Peavy said.
Giants manager Bruce Bochy said there is no target return date for the 34-year-old Peavy, who has made two starts this year and hasn't appeared in a game since April 17.
"He's feeling a lot better with that lower back," Bochy said. "That's good news for us. It looks like he can resume his rehab and hopefully stay away from any more setbacks and get him ready here. It's going to take a few starts for him because he did have a setback here. The good news is that he thinks he's gotten over the hump with what was bothering him."
Peavy isn't the only Giants starter on the mend. Matt Cain, who has been on the disabled list since April 7 due to a flexor tendon injury, was scheduled to throw a 45-pitch, three-inning simulated game in Arizona on Wednesday.
• Bochy held Hunter Pence (left wrist soreness) and Brandon Crawford (calf tightness) out of Wednesday's starting lineup against the Pirates to give them consecutive days of rest with Thursday's visit to the White House.
"You have to be careful when you get in a little streak like we're in right now," Bochy said. "You don't want to keep running your guys out there 'til you get to the point of diminishing returns and wearing them down. Hunter needs a day and Crawford needs a day."
Alex Espinoza is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.