Keith Earls could miss Ireland’s entire autumn campaign due to a hamstring injury.
Munster wing Earls suffered the blow in training Tuesday and has been ruled out of Saturday’s November series opener against South Africa in Dublin.
Andrew Conway has stepped up to start in Earls’ place to face the Springboks, with Darren Sweetnam primed for his Test debut off the bench.
New Zealand-born Bundee Aki will also make his Ireland bow this weekend, forging a formidable centre pairing with Robbie Henshaw.
“Keith picked up the injury on Tuesday, and it was a surprise to him and us,” said Ireland head coach Joe Schmidt.
“It’s a hamstring injury, and I think it’s going to make it certainly a struggle for next week, and potentially the week after.
“So he will be a doubt for the series at this point.
“We’re disappointed and so is he; he was sensational for us in Japan in the summer.
“Not only his on-field actions but the way he led the young players, that was a another role he had fully embraced in this camp.
“He’s the consummate professional, a class player, that rapid acceleration.
“But what a fantastic chance for Andrew Conway and Darren Sweetnam.”