O'Brien ruled out for Ireland
Ireland flanker Sean O'Brien has been ruled out of Saturday's RBS 6 Nations clash with Scotland due to a foot problem.
Munster's Peter O'Mahony will replace the reigning European player of the year with Shane Jennings drafted onto the bench for the match at the Aviva Stadium.
"Sean has a skin infection on his foot which has failed to recover as quickly as expected," read an Irish Rugby Football Union statement.
The attrition rate from Ireland's 17-17 draw with France on Sunday has been high with O'Brien the third player to be made unavailable.
On Monday captain Paul O'Connell and scrum-half Conor Murray were ruled out of the remainder of the Six Nations because of knee injuries.
Ireland's schedule of four games in four weeks - a product of the weather-enforced postponement of their match against France - is stretching their playing resources.
O'Mahony is highly-rated and is a more natural openside than O'Brien, but the 22-year-old has only won two caps as a replacement against Italy and France in this championship.
The more experienced O'Brien came to the fore last season when his explosive ball-carrying made him a central figure for Ireland and Leinster.
The 25-year-old was switched from blindside to openside flanker during the World Cup and continued to bulldoze a path through opposition defences.
While he has not had the same impact in this Six Nations, he is remains a key component of Ireland's vaunted back row.