Johnny Sexton will see a specialist later today over the knee injury he suffered in Saturday's Champions Cup victory over Northampton Saints in Franklin's Gardens.
Sexton came off just five minutes into the second half and the 34-year-old is definitely out of next Saturday's return meeting with the Saints at the Aviva Stadium and will undergo a further scan to determine the nature of the problem.
With the Six Nations only eight weeks away, Sexton's situation will be of concern to new Ireland boss Andy Farrell, who brings his players together for the first time for a brief pre-Christmas camp next week.
The out-half suffered thumb and leg injuries before the World Cup but featured prominently in the tournament and started all three of Leinster's fixtures in Europe this season to date.
Joe Tomane is also ruled out after re-aggravating his hamstring injury and will be out for six to eight weeks, while fellow centre Rory O'Loughlin continues to rehab his shoulder injury.
Meanwhile James Ryan is a doubt for Saturday's clash after picking up a head injury against the Saints at the weekend.
The second row came off late in the encounter and will follow return to play protocols.
Hooker Sean Cronin, who suffered a neck injury in Japan, is fully fit and available, while prop Peter Dooley is also available again after a knee issue.
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