The Portuguese Football Federation (FPF) confirmed Cristiano Ronaldo missed training on Thursday due to an infected toe.
Portugal are currently preparing to defend their UEFA Nations League title, staring with Croatia on Saturday in Porto.
But Ronaldo’s availability has been thrown into doubt after missing training on Thursday. It leaves Portugal with an anxious wait for updates over the next 24 hours.
The FPF released a statement explaining the forward’s absence was down to an infection on his right toe. He spent Wednesday doing gym work and is now undergoing antibiotic treatment.
No further details were released on Ronaldo’s toe problem, but the FPF plan to closely monitor his condition on a regular basis.
Renato Sanches, meanwhile, has suffered muscular problems of late at Lille and will leave the Portugal team camp after medics reviewed his condition.
Portugal are in Group A3 for the Nations League alongside France, Sweden, and Croatia. In such a tricky group, a good start is necessary with only one qualification spot for the knockouts available.
The game against Croatia begins at 20:45 (CET) on Saturday with Sweden coming up next Tuesday afterwards.
Germany and Spain, meanwhile, will kick things off tonight in arguably the biggest fixture of the opening round.