Ireland back row Peter O'Mahony has been ruled out of the World Cup with knee ligament damage and replaced in the squad by Rhys Ruddock.
The 26-year-old Munster flanker had to be taken off 14 minutes into the second half of Sunday's 24-9 win over France.
Team manager Mick Kearney said O'Mahony was "returning to Dublin for specialist opinion".
Skipper Paul O'Connell is to have a scan on a leg injury that could spell the end of his international career.
Fly-half Johnny Sexton is awaiting a scan on a groin problem but Ireland's management said initial clinical assessment was "encouraging" and they were hopeful he would be able to play in Sunday's quarter-final against Argentina.
The loss of the 35-times capped O'Mahony, and probably O'Connell too, leaves coach Joe Schmidt with problems.
Twenty-four-year-old Ruddock - who broke his arm in June - has five caps and would be a like-for-like replacement for O'Mahony at blindside flanker.
Ulster's Iain Henderson, used as a second row in the tournament, is a likely replacement for O'Connell, but he could also come into the back row for O'Mahony, with Donnacha Ryan a possible candidate to partner Devin Toner in the Irish engine room.
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"Paul O'Connell appears to have suffered a significant hamstring injury and was hospitalised overnight. He is having scans to clarify the extent of the injury," added Kearney.
"After an incredibly physical encounter, a host of players are reporting bumps and soreness and will have to be managed, but nothing more serious than that.
"Only Peter O'Mahony has definitely been ruled out. As soon as we have more clarity on the injury front we will be in a position to make decisions on replacement players."
Kearney said Ireland's decision on a replacement for injured centre Jared Payne would be made later on Monday.