Ulster's Pro12 match away to Italian club Zebre on Friday has been called off following the death of Nevin Spence in a farming accident.
The 22-year-old centre died alongside his brother Graham and father Noel in an incident at the family's farm near Hillsborough, County Down, on Saturday.
A moment of silence is to be observed at all of the Pro12 matches being played this weekend. A new date is to be arranged for the fixture in Parma.
The talented player died along with his 30-year-old brother, who was married with two children, and their 52-year-old father.
As well as a book of condolence being opened at Ulster's home in Ravenhill, the IRFU has also encouraged rugby fans to sign a book of condolence at their headquarters at Lansdowne Road in Dublin.