Options include giving Peavy's turn to Ryan Vogelsong or Yusmeiro Petit, or recalling another Minor Leaguer, as the Giants did with Chris Heston.
The most intriguing option Bochy mentioned was doing nothing at all and trying a four-man rotation. Monday's scheduled off-day allows the Giants to employ this plan for about a week. But it's unlikely that they'd subject any of their starters to working on short rest. The first day they'd need a fifth starter would be April 25 at Colorado.
Peavy, of course, will still be on the disabled list at that time. He underwent an MRI on Saturday morning that confirmed a recurrence of the back trouble that forced him to miss a start in the second game of the regular season.
Peavy wasn't certain how much recovery time he would need. He did know, however, that he must heal completely.
"I have some things I have to get right," said Peavy, whom the Giants signed to a two-year, $24 million contract during the offseason. "It's frustrating, of course, but at the end of the day you have to make the right decision -- and it has to be right to help the team moving forward."
Susac's presence will give Bochy more flexibility in deploying personnel. Bochy said he can use either Susac, who hit .350 (7-for-20) in six games at Triple-A Sacramento, or Hector Sanchez as a pinch-hitter. Typically, a lone reserve catcher would have to stay on the bench in case the starting catcher sustains an injury. Susac's arrival also will enable Bochy to use Buster Posey more freely at first base.
"Susac's a guy who's going to be in the mix," Bochy said.
Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.