Connacht centre Hugh Gavin has been ruled out of action until mid-February after undergoing surgery for an ankle injury.
The 20-year-old, who starred during the recent Emerging Ireland tour, suffered the injury on his second senior provincial appearance, against the Dragons at the end of October.
Meanwhile, Pete Wilkins will welcome back hooker Dave Heffernan, and back Santi Cordero, who were on international duty with Ireland and Argentina, respectively, for Saturday's home game against the Bulls (5.30pm, live on RTÉ2).
Peter Dooley (calf) is rehabbing a calf strain and is aiming for a return to selection for the Christmas interpros, while JJ Hanrahan (knee) continues his long-term rehab and remains on track to return in mid-January.
Bundee Aki, Mack Hansen, Finlay Bealham and Cian Prendergast remain in Ireland camp this week ahead of Andy Farrell's side's meeting with Australia on Saturday.
Connacht are fifth in the URC table with three wins from six games, while the South Africa visitors are in third spot.
Follow a live blog on Ireland v Australia on Saturday from 3.10pm on rte.ie/sport and the RTÉ News app. Listen to live commentary on 2fm.
Watch Ulster v Leinster in the URC on Friday from 7.20pm on RTÉ Player.
Watch Connacht v Bulls in the URC on Saturday from 5pm on RTÉ2 and RTÉ Player.
