Mikel San Jose has been struck down by illness and could be forced to sit out Spain's 2012 Olympic campaign as a result.
The Athletic Bilbao defender has been diagnosed with chicken pox.
San Jose was included in Spain coach Luis Milla's preliminary 22-man squad for the London Games.
He has, however, been forced to leave their training camp after contracting the virus.
Milla will be allowed to call up a replacement, but must trim his squad to 18 before Spain begin their gold medal quest against Japan at Hampden Park on 26th July.
Spain have already lost Barcelona midfielder Thiago Alcantara to injury ahead of the tournament.