Michael Hooper's Super Rugby season is in doubt with the NSW Waratahs resigned to losing him for at least a month due to a hamstring injury.
The Wallabies and Waratahs captain suffered the injury during Saturday's third Test against Ireland in Sydney.
Assistant coach Simon Cron confirmed the minimum four-week timeframe on Monday, meaning Hooper's only chance of playing again for the Waratahs would be if the side make the finals.
"I know our physios are working with the Wallaby physios ... but it's very early, so they'll keep working through it," Cron told reporters.
NSW is currently top of the Australian conference on 35 points - only one ahead of the Melbourne Rebels, who they face in a season-defining clash at AAMI Park on Friday night.
The Waratahs then face the Brumbies (home) and Highlanders (away) to complete their regular season.
What to do in Hooper's absence is a question the Tahs have very rarely had to consider, given the 26-year-old's blessed run with injuries throughout his career.
Cron said they were yet to decide who will take over as skipper but suggested Will Miller was the leading contender to fill in at openside flanker.
Miller played at No.6 in their last outing before the June Test window but the return to fitness of Ned Hanigan means he can be moved from there.
Cron admitted the Waratahs would miss Hooper's "massive presence" on the paddock.
"He'll still be here off-field," he said.
"(But) the whole point of us coaching two, three deep is to make sure that when this does happen, other people step into their role.
"We're confident the guys who play behind him, it's now their chance. The door's open, they've got to go. We'll be fine."
The Waratahs may also be without Israel Folau, who faces a judicial hearing for making contact in the air with Irish captain Peter O'Mahony.
Meanwhile, Tolu Latu's strong cameo off the Wallabies bench doesn't appear to have boosted his chances of a start at hooker against the Rebels.
"We've got a big belief in starters and finishers. In baseball, your finishers are the ones who get paid the most," Cron said.
"Tolu came on at the end of the game when it mattered and did a really good job.
"For us, it's probably around what stage of the game do we want Tolu to be playing. It'll be really around horses for courses."