The Leinster star injured his ankle last weekend
Joey Carbery will miss Ireland's two Test matches with Japan.
The Leinster star played against the United States last weekend in New Jersey but left the field early in the second half, with an ankle injury.
Despite the win, it was a tough night for Carbery, who had to kicks charged down, which resulted in American tries. He also missed two of his his five kicks at goal.
While Carbery's injury will come as a blow, Paddy Jackson will be expected to slot in immediately. The Ulster fly-half missed the game in New Jersey for personal reasons, but he joined the squad in Japan ahead of the forthcoming Test matches.
No replacement will be called into the squad, despite the lack of depth. Last weekend, Rory Scannell made his debut off the bench, and will be expected to be Jackson's understudy in Japan.