Darron Gibson has fractured a toe and is doubtful for the Republic of Ireland's back-to-back European qualifiers against Germany and Cyprus next month.
The 19-year-old Derryman suffered the injury today while playing for Manchester United's reserves in a game against Sporting Lisbon.
There has been no official confirmation from the club as to how long Gibson will be sidelined but early estimates suggest at least three weeks.
That would leave the midfielder short of fitness ahead of Germany's visit to Croke Park on October 13th and then the game against Cyprus four days later.
Gibson has been the focus of tension between the FAI and IFA since defecting to the Republic four years ago.
He played for Northern Ireland at underage level before switching to the Republic for an under-17 European qualifier.
The teenager has since worked his way through the Republic's underage ranks and featured in the recent senior friendly win over Denmark before making his competitive debut against Slovakia 11 days ago.
Steve Staunton's team, meanwhile, have climbed five places to 32nd in the latest Fifa world rankings released today. The team leapfrogs Northern Ireland who sink nine spots to 36th.
England and Scotland are both rewarded for positive results in recent qualifiers.
Steve McClaren's men return to the top 10 for the first time since June, sitting in ninth spot. The Scots are rewarded for their famous victory over France in Paris by surging forward nine places to 14th.
World champions Italy lead the standings after jumping two places after a victory over Ukraine and a draw with France. They replace Brazil, who fall to third behind Argentina.
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