Ireland and Ulster forward Iain Henderson will miss between 10 to 12 weeks of action after he underwent a surgery on his thumb.
Henderson, who starred in Ulster's 30-15 victory over Scarlets at Kingspan Stadium in the previous round after scoring two tries decided to attend the issue on his thumb with the World Cup lined up next year.
As a result, the 26-year-old will be sidelined for up to three months that will force him to miss the majority of Six Nations for Joe Schmidt's side at the start of the next year but could be available for the final two rounds against France and Wales.
Henderson has played 42 Tests for Ireland since his debut in 2013 and recently was part of the clash against USA at Lansdowne Road during the November series.
Meanwhile, Matthew Rea, who suffered a thumb fracture while featuring for his club Ballymena last weekend also underwent a surgery and will be sidelined for up to 10 weeks.
Ulster are currently third in Conference B table of Pro 14 and will face Munster Rugby in the next round at Kingspan Stadium scheduled on 22nd December after a successful run in European Champions Cup that saw them complete a double over Scarlets.