The Leinster centre is believed to be struggling with a hamstring injury and Ulster’s Will Addison has been stood down from the province’s squad to take on Glasgow Warriors in a pre-season friendly.

Addison was close to making the original squad.

A versatile back, he would be the obvious replacement for Henshaw who has suffered a stream of injuries in recent times and only started the last of Ireland’s four warm-up games, against Wales last weekend in Dublin.

The fact he was superb in that game reiterates his importance to the team but the full extent of Henshaw’s problem is yet to be revealed.

Ireland are due to hold their first official press conference in Japanese soil at 9am local time on Sunday morning (1am Irish time).

They play their first game in Pool A, against Scotland, next Sunday, September 22.