Steve Finnan could be forced to pull out of the Republic of Ireland squad for the Euro 2004 qualifiers against Georgia and Albania.
The Fulham right-back sustained an injury to his left side in the Cottagers' friendly with West Ham earlier this month.
Finnan, who missed Saturday's 2-2 draw with Southampton, has been scanned and club physio Jason Palmer does not believe he has fractured any ribs.
But he is definitely out of the trip to Old Trafford on Saturday morning and will make a decision after the weekend on his participation in the Republic's fixtures in Tblisi next Saturday and in Tirana a week on Wednesday.
Finnan also missed the Republic's 2-0 friendly success against Scotland last month, new manager Brian Kerr's first match in charge, through injury.