Fulham are waiting for the results of a scan on Damien Duff's calf following a freak injury.
Duff was just 9 minutes into the game against Arsenal on Sunday when he had to be substituted.
"He felt something go in his calf," said Fulham manager Roy Hodgson.
"We won't know how serious it is until we get the results of a scan.
"There was no one near him when he went down, it's just one of those freak situations."
It means that Duff could important club and country matches if the news is bad.
Fulham play Basle this week in the Europa League followed by West Ham in the Premiership on the weekend.
Ireland have a World Cup Qualification clash against Italy at Croke Park next month.
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