Jonny Sexton has been ruled out of Saturday's return game against Saints due to the injury he picked up at Franklin's Gardens last weekend.
The Leinster and Ireland fly-half was forced off five minutes into the second half with a knee problem and will play no part in the second leg of the Champions Cup double-header.
Ross Byrne came on for Sexton last weekend and enjoyed a successful cameo, scoring two minutes after being introduced and also adding two conversions to his team's tally.
And Byrne looks likely to deputise at the Aviva Stadium on Saturday evening.
James Ryan could also be missing for Leinster as the Ireland lock is now following concussion protocols after leaving the field at the Gardens before full-time.
Joe Tomane did not play last weekend and the centre will be unavailable on Saturday as he has re-aggravated his hamstring injury.
Rory O’Loughlin is another player ruled out as he continues his rehab following a shoulder injury.
But Peter Dooley and Seán Cronin have returned to full training following knee and neck injuries respectively.
There was no update on long-term absentees Vakh Abdaladze (back), Jack Conan (foot), Barry Daly (knee) and Dan Leavy (knee).