Robbie Henshaw's availability for the World Cup opener against Scotland on Sunday week and the entire tournament is under threat after the 26-year-old is believed to have suffered a hamstring injury.
In a cruel twist, Henshaw also missed the tournament opener in 2015.
Henshaw and Bundee Aki were set to continue the midfield pairing that performed so well against Wales in the final warm-up game.
Garry Ringrose is now expected to wear the number 13 against Scotland.
Should Henshaw be ruled out entirely, Ulster’s Will Addison would be next in line to join the squad. The versatile 27-year-old was taken out of the Ulster team to play Glasgow in a pre-season game at Scotstoun on Saturday afternoon.
More information will be available on Henshaw when Ireland coach Joe Schmidt speaks to the media at their Chiba base on Sunday morning.
