Leinster captain Johnny Sexton has been ruled out of Saturday's Champions Cup game at home against Northampton Saints with a knee injury.
The Ireland fly-half was forced off in the 44th minute of his side's impressive 43-16 win at Franklin's Gardens last weekend.
The extent of the injury is not yet known, with Sexton, 34, set for a scan on Monday afternoon.
Leinster will be able to call on hooker Sean Cronin, who has been passed fit.
The Ireland international has not featured for the province this season having picked up a neck injury that prematurely ended his World Cup campaign.
Injuries to Sexton and centre Joe Tomane, who is set to miss at least six weeks with a hamstring issue, were the only downsides for Leinster as they romped to a seven-try victory over English Premiership leaders Northampton.
The win opened up a five-point lead at the top of Pool One for last year's runners-up, and another win on Saturday in Dublin could secure Leinster's quarter-final berth if Lyon failed to defeat Benetton.