Team doctor Jorge Guillen recommended that Muniain sits out the Group D game against Japan on Thursday after reviewing the results of an MRI conducted in Glasgow. That would leave Spain without one of its most creative players.
Guillen said Wednesday the 19-year-old Muniain should train a few more days before playing a game. Initially, the medical team thought the forward had torn a muscle in his thigh, but Guillen says it looks more like a strain.
Muniain should be ready for Spain's match against Honduras on Sunday in Newcastle.