Whitlock (knee) threw from flat ground Thursday but has been shut down after experiencing discomfort, MLB.com reports.
Whitlock attempted to throw after getting a pain-killing injection, but it appears he starting throwing too soon. As a result, the right-hander will be shut down for a period of three or four days. Despite the setback, the club believes his stay on the 15-day injured list should be for the minimum amount of time. Whitlock is eligible to return June 9.