Bay left Saturday's game at Baltimore in the sixth inning with a cramp in the hamstring. He expects to start in Wednesday's game.
"Give it one more day, probably the smart thing to do," Bay said. "It feels a lot better than it did yesterday."
J.D. Drew, slowed by a groin strain, started in right field. He felt OK after running before the game.
Knuckleballer Tim Wakefield, out since July 18 with a lower back strain, said he will throw a bullpen session Wednesday. While his back has greatly improved, Wakefield said a nerve irritation has caused discomfort in his calf.
"Throwing a side for the first time and going from there," Wakefield said. "My biggest hurdle right now, I think, is fielding my position."
Pitcher Daisuke Matsuzaka, on the disabled list since June 20 due to a right shoulder strain, threw at 120 feet and is scheduled for his initial bullpen session next Tuesday or Wednesday.
"He looked good," Boston manager Terry Francona said.
First baseman Jeff Bailey (left ankle sprain) has started a minor league assignment with Triple-A Pawtucket.