Bochy indicated that determining whether Peavy or Matt Cain would switch to relieving wasn't a decision arrived at quickly.
"It's never easy to tell a veteran to make a role change," Bochy said.
However, recent results spurred Bochy's choice. After posting a 1-5 record with an 8.21 ERA in his first nine starts, Peavy found a groove and went 4-2, 2.45 in his next eight outings. Yet his recent fortunes have swung in the other direction. He's 0-2 with a 6.98 ERA in his last four starts and has allowed six homers in his previous three games.
By contrast, Cain has won each of his last two starts. His performance was uneven against Cincinnati on July 26, when he yielded four runs and six hits, including two homers, in 5 1/3 innings. But he was considerably stronger Sunday, no-hitting Washington for five innings before an inflated pitch count forced him from the game.
"You look at Matt's last couple of outings, they've been encouraging," Bochy said. "He's close to what he was before he hurt his hamstring."
Bochy also suggested that warming up quickly, which is required for a reliever, is "going to be a little bit easier for Jake."
Bochy said Peavy accepted the role change unhesitatingly, which the 14-year veteran confirmed by saying he felt "too grateful to be hateful." It happened to be Grateful Dead night at Citizens Bank Park.
• The Giants made myriad player moves to reset their roster due to injuries and the wake of the non-waiver Trade Deadline.
Left fielder Mac Williamson went to the 15-day disabled list with a left shoulder strain, resulting from his tumbling attempt to make a catch in Sunday's game against Washington. Infielder Ehire Adrianza, sidelined virtually all season with a fractured left foot, was activated from the disabled list.
Roster room for Moore and reliever Will Smith was created as left-hander Matt Reynolds and right-hander Albert Suarez were optioned to Triple-A Sacramento.
Also, infielders Grant Green and Ruben Tejada cleared waivers and were assigned to Triple-A.