Wallaby star David Pocock, a possible captaincy candidate, is almost certain to be ruled out of the British and Irish Lions series later this year.
Pocock suffered a serious knee injury in the Brumbies' 35-6 demolition of the Waratahs in Canberra on Saturday.
He went for scans, after limping off the field in the 13th minute.
He was later spotted with an ice pack on the injured limb, with early reports suggesting he damaged the anterior cruciate ligament (ACL) in his left knee - which could rule him out for up to six months.
"Not the best news with the scan," Pocock said on his official Twitter page.
"I'm going to have to see the surgeon Monday," Pocock added.
Rated as the "premier open side flank in the world" by his replacement on the day, George Smith, Pocock will now anxiously wait the outcome of his visit with the surgeon to hear how long he will be sidelined for.
Smith, a legendary Wallaby before his departure to Europe and most recently to Japan, didn't shy away from his earlier than expected return to the field, dominating the breakdown and showing he still has what it takes to compete at Super Rugby, and perhaps international level.
Smith said it was the physicality of the match, not his fitness, that was the major difference between the Japan league and Super Rugby.
"Obviously I'm not tackling 115kg guys in the Japan league week in, week out," he told AAP.
Brumbies coach Jake White said it was too early to predict whether or not Pocock's season was over, but conceded how fortunate it was the Brumbies had signed Smith recently to play most of the Super tournament in the off-season for his Japanese club.
"It shows you how fate plays out ... it's just fantastic how things have worked out now that George has arrived," White said.
If Pocock's ligament is ruptured, he has two options - a traditional reconstruction with a recovery time of nine months or he could opt to have the revolutionary LARS surgery which could have him back on the field in 12 weeks.
If he has LARS, he could conceivably be back in action by the start of June and play some role in the Lions series.
Deans said last week he was not considering luring 110-Test veteran Smith back to the international arena. But should the 32-year-old recapture the form with which he dominated the competition for a decade, he looms as an attractive option for both Deans and Brumbies coach Jake White.
Smith has signed a short-term deal with the Brumbies and is supposed to return to his Japanese club duties with Suntory at the end of May.
However, it's understood there is some room for negotiation for his return date and a Wallabies jersey could convince him to stay for an extra month.
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