Mostert told Nick Wagoner of ESPN.com after Saturday's win against the Vikings that he exited in the fourth quarter due to a cramp in his calf.
According to Mostert, he was treated with an IV and added that he dealt with "some sickness" during the week. Niners injury reports prior to the game didn't mention his name at all, but in any case he expects to be fine moving forward. On Saturday, Mostert took a back seat to Tevin Coleman (22 carries for 105 yards) out of the backfield but still contributed 58 yards on 12 rushes and recovered a muffed punt.