Ireland flanker Sean O'Brien will miss the next Six Nations match against England at Twickenham due to a hamstring injury.
Ireland coach Joe Schmidt confirmed the decision on Monday.
Winger Dave Kearney is also very doubtful for the game on February 27 with a shoulder injury and lock Mike McCarthy (concussion) and centre Jared Payne (hamstring) are also struggling to be fit.
Flyhalf Johnny Sexton, however, should be available after recovering from a whiplash injury.
"He is feeling a lot better," Schmidt told the Irish Rugby Football Union website.
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Ireland, Six Nations champions for the last two years, drew with Wales in their opener and lost 10-9 in France on Saturday.
