Ireland's Luke McGrath looks set to miss the entirety of the Six Nations after he was ruled out of action for up to eight weeks with a knee ligament injury.

McGrath went off injured while on Champions Cup duty with Leinster last weekend and the province's scrum coach John Fogarty confirmed the diagnosis.

That leaves McGrath with a return date in mid-March and with Ireland's final Six Nations game away to Wales on 16 March, the scrum-half would appear to be almost certain to sit out the tournament.

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It also means that McGrath will miss Leinster's Champions Cup clash with Wasps this weekend, as will Johnny Sexton, although his injury is nowhere near as serious.

Speaking to RTÉ Sport, Fogarty explained: "Unfortunately for Luke he’s picked up a knee ligament injury against Toulouse and he’s going to be missing for up to eight weeks so we’re disappointed for Luke.

"On the other front Johnny is not quite there. He’s rehabbing a tendon issue that he’s had in his knee and he’s just not quite there.

"He’s close, he’s been very close but unfortunately I think the week isn’t long enough for us and he’s run out of time a little bit, which is disappointing for us but Ross [Byrne] has been doing very well and he’ll step in and hopefully do a good job.

"We want to make sure we’re giving the players the best opportunity to perform for us and for the national team as well, so it’s with that in mind that we’re making sure the players are in the best health so they can do that."

There's good news elsewhere for the province however, with Devin Toner, Robbie Henshaw and Sean O'Brien all returning to full training this week.

Meanwhile Leinster have registered scrum-half Paddy Patterson for their Champions Cup squad, replacing Nick McCarthy. 

Victory for Leinster at the Ricoh Arena would see them guarantee that they finish top of their pool and earn a Champions Cup quarter final at the RDS Arena.