McDonald was eligible to be activated Tuesday, but he isn't where the team wants him to be physically.
"Today he said he could play, but he's not 100 percent and I told him I'd like him to be 100 percent, being he's on the disabled list," manager Bobby Valentine said. "And by the time he comes back, we'd like to have a player who's capable to go full bore."
McDonald went 0-for-3 and was hit by a pitch in Triple-A Pawtucket's 6-4 loss to visiting Norfolk on Monday. He's 0-for-8 in three rehab games with two strikeouts and no walks.
Pawtucket is home through Thursday playing Norfolk before going on the road.