The Red Sox placed Whitlock on the 15-day injured list Thursday with right elbow inflammation, Chris Cotillo of MassLive.com reports.
Manager Chad Tracy revealed that Whitlock was unavailable to pitch in Wednesday's loss to the Blue Jays because of a sore elbow, and the club has opted to put the reliever on the IL. Whitlock noted Wednesday he has a "very low" level of concern the injury is serious, but the Red Sox could send him for imaging just in case.