Andres Iniesta could miss Spain's FIFA Confederations Cup campaign after suffering a recurrence of his thigh injury.
The 25-year-old playmaker was doubtful for Wednesday's UEFA Champions League final with the same problem.
And although he won his race to be fit in time for Barcelona's 2-0 win over Manchester United, Iniesta aggravated the injury during a stand-out performance in the European showpiece.
Barca coach Pep Guardiola has confirmed Iniesta will be available to travel with the Spain squad to South Africa but has urged the international set-up to exercise caution.
"All those Barcelona players that have to go the Confederations Cup will go, but be careful with Iniesta," he said.
"In the Champions League final he had a relapse on his injury and it's in a very complicated place.
"If it's not treated properly it could be difficult for him, for Barcelona and for Spain."
Spain coach Vicente del Bosque is set to name his squad for next month's Confederations Cup on Monday.
The European champions will face Iraq, New Zealand and hosts South Africa in Group A, and potentially Brazil and Italy in the latter stages.