McClure returned in time for Aaron Cook's second start of the year. The right-hander started Sunday's game in place of Clay Buchholz, who was placed on the 15-day disabled list with an undisclosed illness.
"We've got to get him caught up is all," said manager Bobby Valentine. "Once he gets caught up he'll be right in the swing of things."
During McClure's absence, the club's rotation has undergone a few changes.
Cook was activated from the 15-day disabled list on Sunday. Last Sunday, Franklin Morales made his first start since 2009 in place of Josh Beckett, who is on the DL with inflammation in his right shoulder. Morales struck out eight in six innings on Saturday vs. the Braves in his second outing to win his first game as a starter with the Sox.
Valentine described his rotation as "a work in progress" on Sunday.
"We'll get Bob in that loop and see if he has any ideas," Valentine said.