Ireland prop Andrew Porter has been ruled out of the remainder of the Six Nations due to an ankle issue.
The 26-year-old limped off early in the second half of Sunday’s 57-6 win over Italy in Dublin.
Ireland return to action away to title rivals England on Saturday, March 12 before completing the championship seven days later at home to Scotland.
Porter has been in fine form for Andy Farrell’s side, successfully switching from tighthead to loosehead this season.
Forwards coach Paul O’Connell admits the Leinster player’s enforced absence is a major blow.
“He’s a big loss, he’s a modern prop forward,” said O’Connell.
“He’s an excellent scrummager on both sides of the scrum but his ball-carrying, his defending for us, really good poacher, a great man for turnovers, getting penalties for us at the ruck.
“He’s no-nonsense to coach. He just gets on with it, he’s very easy to coach, easy to deal with so he’ll be a big loss. His bench (press) will probably go through the roof in this period, which he’ll be delighted with.”
Porter is the second member of the Irish front row whose Six Nations campaign has been ended by injury after hooker Ronan Kelleher sustained a shoulder problem in the round-two defeat away to Grand Slam-chasing France.
The Irish Rugby Football Union has confirmed Porter – who was selected by the British and Irish Lions last summer only to miss out due to a toe issue – will return to his province for medical treatment following the results of his scan.
Leinster’s Cian Healy and Munster’s Dave Kilcoyne are in contention to replace Porter at Twickenham, having each featured off the bench during the tournament.
O’Connell also said there was a possibility an additional prop could be added to the squad after the weekend.
“There is no doubt a guy like Andrew Porter – he is first choice at the moment – is a loss; but it is a great opportunity for the guys, for Cian, for Dave,” said O’Connell.
“Dave Kilcoyne started the game against England 12 months ago (a 32-18 win in Dublin), he went off quite early.
“Cian came on and had a really good game, so there is great experience there. It is a great opportunity for these guys as well. They are real enthusiastic guys and they want the opportunity to play.
“We are very happy with what we have behind Andrew Porter. The way we’ve been training, a lot of the changes have been seamless enough and easy enough so hopefully it continues that way.”
Meanwhile, centre Robbie Henshaw has returned to training after satisfying head injury protocols.