Ireland are looking short at scrum half ahead of the Six Nations.
Scrum half Paddy Patterson has been registered to Leinster’s Champions Cup squad, taking the place of Nick McCarthy.
John Cooney also pulled out of Ulster’s Champions Cup game against Racing 92 on Saturday with a back complaint.
It means that Munster’s Conor Murray is the only fully fit scrum half among Ireland’s leading number 9’s.
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Johnny Sexton will also be missing Leinster’s trip to Wasps as he continues to recover from his own knee injury but is expected to be back in the fold imminently.
“Johnny has been rehabbing a tendon in his knee and the week’s not long enough, he just ran out of time,” said Leinster scrum coach John Fogarty. “He’s not far off at all but unfortunately for us, he’s run out of time.
“We’ve made the decision, so Ross [Byrne] is there to cover. For Johnny, I don’t see it being a huge issue for him going forward. He just needs to be in the right space physically so he can perform.
“That’s our focus here, we want our players to be in the best physical condition so they can perform for us and for the national team. Johnny will get himself right and will be back.”
Devin Toner (ankle), Sean O’Brien (arm) and Robbie Henshaw (hamstring) will all return to full training this week, while Fergus McFadden (hamstring) begins a lighter schedule.
Rob Kearney (quad) and Dan Leavy (calf) are to undergo further assessment.
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