Wales scrum-half Tomos Williams faces four months out after damaging his shoulder.
The 25-year-old suffered the injury during Cardiff Blues' Guinness PRO14 defeat to the Scarlets on Saturday and will now undergo surgery.
The Blues said on their website that Williams will be out for an "estimated three to four months".
The injury rules the 20-times capped Williams out of Wales' autumn programme.
Wales are due to face Scotland on 31 October in their remaining 2020 Six Nations fixture, the game postponed in March because of the coronavirus pandemic.
Wayne Pivac's side are then set to feature in a still to be confirmed eight-nation tournament. 261303 AUG 20