Munster have confirmed that Conor Murray, Malakai Fekitoa, RG Snyman and Calvin Nash have been ruled out of Saturday's URC semi-final encounter with Leinster at the Aviva Stadium (5.30pm).
The quartet suffered head injuries in last Saturday's 14-5 quarter-final victory over Glasgow Warriors in Scotstoun.
Munster skipper O'Mahony was forced off after just four minutes of the game with what the province are describing as an elbow injury and the 33-year-old will undergo a scan today.
READ MORE: Munster sweat on key men as Scotstoun victory paves the way for semi-final shot at Leinster
If he receives good news, O'Mahony could feature as Munster chase their first silverware since 2011, but they are up against it having only won one of their last 10 meetings with their rivals.
Better news for head coach Graham Rowntree is that Tadhg Beirne suffered no issues on his return from an ankle injury that has kept him out since Ireland's win against France in February.
Beirne took on the captaincy after O'Mahony came off and the Kildare man played the full 80 minutes.
Meanwhile, Diarmuid Barron (shoulder) will be reviewed as the week progresses to determine his availability.
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