The injury occurred during training on Thursday, although Milan said it was not serious.
Gattuso had been battling a nerve problem affecting his left eye and hasn’t played since colliding with teammate Alessandro Nesta in the Serie A opener on Sept. 9. He resumed training last month.
Meanwhile, the extent of midfielder Antonio Nocerino’s left thigh problem won’t be known until Friday. Nocerino exited during the first half of Milan’s 2-2 draw with Plzen in the Champions League on Tuesday.
Two points behind Italian league leader Juventus, Milan visits Bologna on Sunday.