The San Diego Padres' ace, who felt discomfort in his right elbow the last three or four starts, had an MRI exam Monday.
"In this case, I'd say more than likely Jake could be missing more than one start," Manager Bud Black said.
Peavy had been scheduled to start Monday night but was scratched Sunday.
Pedro Martinez threw 4 1/3 innings of a simulated game and the New York Mets plan to have him throw a bullpen session Wednesday or Thursday in Atlanta. Martinez, who has been out since straining his left hamstring April 1, threw 77 pitches.
Atlanta Braves ace John Smoltz still has discomfort in his right shoulder, leaving him unsure when he'll be able to pitch again. Smoltz has been on the disabled list since April 29. He hopes to learn more after throwing on the side today.
The 41-year-old Smoltz reported problems after his bullpen sessions Thursday and Saturday. He has a long history of pitching well while dealing with mild discomfort and said that if all goes well today, his plans for a minor league rehab stint this month "could very easily fast-track."
The Kansas City Royals reinstated catcher John Buck from the bereavement list and optioned catcher Matt Tupman to triple-A Omaha. . . . The Oakland Athletics put infielder Donnie Murphy on the DL because of a sore right elbow and recalled left-hander Dallas Braden from triple-A Sacramento.