Fox left the Kings' 105-104 overtime loss to the Minnesota Timberwolves in the opening quarter Thursday with what the team called back spasms. He is being listed as day-to-day.
Forward Marvin Bagley III also left Thursday's contest with a left foot injury. He will be evaluated by a foot specialist Saturday, the team said.
Fox, in his third season out of Kentucky, is averaging a career-high 17.6 points per contest this season, while shooting a career-best 46.5%. The Kings entered Friday with a 12-19 record and 1½ games out of eighth place in the Western Conference.