Kevin De Bruyne is likely to miss Belgium's Euro 2020 opener against Russia on June 12, says Roberto Martinez.
De Bruyne suffered facial fractures in a challenge with Chelsea defender Antonio Rudiger in Manchester City's Champions League final defeat on Saturday.
The midfielder does not require surgery but Martinez is not sure when the 29-year-old will be available for selection.
When De Bruyne does return, the Belgium boss confirmed he will be fitted with a mask similar to the one worn by team-mate Jan Vertonghen after he was injured playing for Tottenham two years ago.
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"De Bruyne is unlikely to be fit for that first match so whoever replaces him will have to show he's ready," Martinez said on Wednesday.
"We made a decision about his mask. It will be one of the producers who made Jan Vertonghen's mask. We were very satisfied with that.
"I would say that until next week we won't know exactly where we are with Kevin. Now, allow him to relax.
"He could be available for the Euros but we don't know when at the moment. It's too early to give you an answer now, we must first get the green light from the medical side."
Belgium open their Euro 2020 campaign against Russia in St Petersburg next Saturday.
The world's No 1-ranked side then face Denmark on June 17 before playing Finland in their final match of Group B on June 21.