The veteran McCann has been bothered for most of the season with discomfort in his right shoulder caused by a cyst.
McCann received a cortisone shot after Saturday night's loss to the Phillies, then missed each of the next three days. He returned to the lineup on Wednesday with the hope that the latest injection proves to be more beneficial than the one he received on Aug. 7.
McCann has batted .228 with 18 home runs and a .702 OPS in 104 games. It appeared he might have righted himself when he batted .296 with nine home runs and a 1.059 OPS in July, but he batted .181 without an extra-base hit in August.