Ulster second row Dan Tuohy sustained an injury to his right arm in the Province's 26-9 victory over Cardiff Blues in the Arms Park last night.
A scan today revealed that his arm is fractured and that he will require surgery.
It's expected that he will be out of rugby for up to 12 weeks.
The injury is a repeat of the fracure he suffered playing for Ireland against Wales in the Six Nations earlier this year.
Ulster defence coach Jonny Bell said: "Dan has been immense for us so far this season and has become our top try scorer.
"The injury is in the same arm in which he had a plate inserted following a previous injury and it doesn't look good."
