The Ireland fly-half limped off in the 44th minute of the Round 3 success at Northampton last Saturday with a knee injury.

He will join centres Joe Tomane and Rory O’Loughlin on the sidelines. Australian Tomane has aggravated his hamstring injury and will now be out of action for six to eight weeks, while O’Loughlin is rehabilitating following a shoulder injury.

Lock James Ryan, who was removed late in the second half against Northampton Saints with a head injury, will follow the graduated return to play protocols under the supervision of team medics.

There was some good news for head coach Leo Cullen, though. Both prop Peter Dooley and hooker Seán Cronin have returned to full training following knee and neck injuries respectively.

However, the 41-year-old was keen to look ahead to this week’s Round 4 fixture in Dublin, warning that his Leinster side have been in a similar position before and struggled with home advantage.

"We've been in this situation before where we've had a big win in Northampton and gone back to the Aviva been beaten,” Cullen said.

"You have to be so careful with these fixtures. Normally, it's just onto the next team. It's a unique thing that takes place in the season where there's head-to-head fixtures. It doesn't always transfer into the following week.

"We've seen that first-hand ourselves in this exact fixture where we've had a win - similar to what we had on Saturday - and then go back to the Aviva the following week and Northampton were very clever that day.”

Heineken Champions Cup Pool 1 leaders Leinster Rugby will be without experienced playmaker Johnny Sexton for their return match with Northampton Saints at the Aviva Stadium on Saturday.