Robbie Henshaw is set to miss Ireland's World Cup opener against Scotland after coach Joe Schmidt confirmed that he suffered a hamstring injury in training this week.
The 26-year old centre has been heavily afflicted with injuries in recent years and has missed the bulk of the past two Six Nations campaigns.
"Robbie pulled up with a bit of tightness in his hamstring," confirmed Schmidt.
"He has a scan at 2pm (Japan time). That will give us more information.
"When he pulled up he wasn't accelerating. We’d be hopeful it is not be too bad.
"Is it likely to rule him out of this week? Yeah, you would have to say it is likely, the fact that he did pull up but we’d be hopeful it is not too bad. I don’t want to guess until we get the scan."
Will Addison is on standby to receive a call-up if Henshaw is ruled out the tournament.
The utility player was due to start Ulster's pre-season clash against Glasgow Warriors at full-back yesterday, but was moved to the replacements bench before kick-off and was not used by the province in a 36-33 defeat at Scotstoun.
"No, he is not on his way over," said Schmidt. "That was precautionary just to make sure that we had fit and able cover should we need a replacement for Robbie."
Henshaw's injury is a significant blow for Joe Schmidt as the Leinster man had recovered from his recent setback and delivered a fine display in Ireland's emphatic victory over Wales in their final World Cup warm-up game last Saturday.
It is now anticipated that Garry Ringrose will start at outside centre in the World Cup opener against Scotland.
Follow Ireland v Scotland on Sunday (kick-off 8.45am) via the live blog on RTÉ.ie/Sport and the News Now App, watch live on RTÉ2 from 8am or listen to live match commentary on RTÉ Radio 1.