Peavy has dealt with back stiffness early this season and was knocked out of his start on Friday against the Arizona Diamondbacks after 3 2/3 innings. Peavy allowed four runs on eight hits in the Giants' 9–0 loss.
Peavy acknowledged that though his back would require "a little treatment," he refused to use physical discomfort as an excuse for his subpar outing.
"I was plenty good enough to be out there," said Peavy, whose five-game winning streak against Arizona dissolved. "I have to help my team more than I did tonight."
Peavy also allowed four runs on four hits in his first start of the season, a four-inning outing in a 6–4 loss to the San Diego Padres on April 12. Over his two starts, the 33-year-old has a 9.39 ERA with seven strikeouts and four walks over 7 2/3 innings.
The defending World Series champions signed Peavy to a two-year, $24 million deal in December.
The Giants (3–9) entered Saturday's game against the Arizona Diamondbacks on an eight-game losing skid.
- Mike Fiammetta