Ireland wing Keith Earls has been ruled out for six weeks with a torn hamstring sustained in training during the week.
It is bad luck for Earls who has been in sparkling form for his country of late, having scored nine tries in his last 10 matches for Ireland.
Earls did the damage in training on Tuesday and Ireland coach Joe Schmidt admits it does come as a blow seeing that he has been in such fine form.
“He picked it up on Tuesday, and it was a surprise to him and us,” Schmidt said of the injury.
“It’s a hamstring injury, and I think it’s going ot 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 because 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."
Schmidt has opted for the experience of Rob Kearney at full-back over the youthful exuberance of Joey Carbery and when asked for his thinking behind his decision, Schmidt said: “This time last year I think people were questioning Rob’s involvement, but I don’t think we’d have won in Chicago without him.
“Those are the attacking threats in the air and on the ground, it’s that experience. For those guys in the back-three I think Rob’s going to be really important, helping to navigate those guys around the pitch.
“First of all, form players, we wanted to reward players who had been going well for their provinces, and then add a bit of experience. And I think we’ve got both.”