Ireland loosehead prop Cian Healy will play no part in this weekend's rematch for Leinster against Northampton Saints in Dublin.
Healy suffered an ankle injury in the 40-7 win over the English side at Franklin's Gardens last Saturday.
The 26-year-old is not expected back until January according to the Irish Times, keeping Healy on the sidelines during the upcoming festive season.
Rising star Jack McGrath is now set to start in Healy's place.
Other injury concerns include Sean O'Brien (dead leg) and Issac Boss (hamstring), but both players are expected to be available for selection this weekend.
Leinster currently top Pool 1 ahead of Castres, Saints and the Ospreys - with a five-point gap between the three-time champions and second-placed Castres.