Manager Kevin Cash said McClanahan (triceps) won't make his rehab start as scheduled Thursday due to biceps soreness, Ryan Bass of FanDuel Sports Network Sun reports.
The Rays will be "pulling back" on the left-hander's throwing for a few days, though it's worth noting that the biceps issue isn't believed to be related to the nerve problems in his triceps that landed him on the injured list in late March. McClanahan appeared to be tracking toward making his season debut in early August, but it's unclear how long the setback will delay his return.