Merkin Valdez (elbow) has suffered another setback in his recovery and won't begin a minor league rehab assignment as scheduled this week.
Valdez complained of soreness Tuesday. "We're going to have to find out what's going on," manager Bruce Bochy said.
The Giants are expected to make a decision on whether Noah Lowry (arm) should attempt to start throwing again.
Lowry hasn't pitched in a month since feeling tingling in his surgically repaired left arm. "He feels good. He's getting stronger," head trainer Dave Groeschner said. "We're going to bring him back after the break and talk about whether he can play catch or not. I know he wants to. We'll see where his strength is."
Dave Roberts has gone 3-for-9 with a double, a triple, a homer and three RBI in the first three games of his minor league rehab assignment.
The strong start could have Roberts back sooner than the original estimate, which saw him needing 40-50 at-bats in the minors. Still, team sources tell the San Francisco Chronicle that Roberts won't be inserted back into left field over Fred Davis, but will instead be used as a left-handed bat off the bench.