Ulster flanker Stephen Ferris has been rated a major doubt for Sunday's Heineken Cup quarter-final against Munster because of an ankle injury.
The Ireland and Lions star limped off during the first half of Friday's Pro12 win over Aironi on Friday night.
A scan on Monday revealed that Ferris had significant ligament and muscle damage, making him unlikely to be fit for the Thomond Park showdown.
The loss of Ferris would be a huge blow to Ulster's prospects.
If he is ruled out, it would be the second year in a row Ferris has missed the European quarter-finals.
A serious knee injury, sustained against Aironi, forced him to sit out the 2011 last eight defeat away to Northampton.
If Ferris is ruled out, Willie Faloon, who came on for Ferris against Aironi, is expected to be drafted into the starting line-up with Chris Henry switching to blindside flanker.
Munster appear to have better news on the injury front with Paul O'Connell, Conor Murray, Donnacha Ryan and Keith Earls are expected to be available.
O'Connell and Murray have both been out of action since sustaining knee injuries in the Six Nations clash against France but have returned to training along with Donnacha Ryan.
Keith Earls is also set to be fit after sustaining a knock in Saturday's defeat by Leinster.
