Wallabies captain Stirling Mortlock has ruled out an early return to the Super 14 from shoulder surgery as an injury crisis forces the Brumbies to field their most inexperienced backline ever.

The Brumbies suffered a major blow with the loss of powerhouse Wallabies back Adam Ashley-Cooper for almost half the Super 14 season in last Saturday's 34-3 opening round loss to the Crusaders in Christchurch.

Ashley-Cooper sustained a high ankle strain in the first half of the match which is expected to keep him out for six weeks.

The 23-year-old utility was among the brightest sparks for Australia in 2007 and was seen as a key figure for the ACT-based franchise as skipper and outside centre Mortlock recovered from shoulder surgery.

Mortlock returned to training in Canberra but reconfirmed he won't be back at outside centre until the middle of the competition, which is the time Ashley-Cooper is also expected back.

"A few of the boys today have given me the call to arms but my rehab's on a pretty regimented program and I'll be hopefully progressing as quickly as possible without pushing it too much," Mortlock told reporters.

"The shoulder's on track, it's going very well but I don't think there's much reason for me to push it too much.

"I would absolutely hate it if I pushed it and did some more damage.

"There's no way I want to do that. I want to tick off all the boxes and by the time I'm ready to come back I'm very, very confident that my shoulder will be as good as new."

Ashley-Cooper's loss with syndesmosis has been further complicated by a neck injury to inside centre Gene Fairbanks, leaving coach Laurie Fisher contemplating the selection of a rookie midfield combination.

Anthony Faingaa and George Smith's younger brother Tyrone are being sized up for the centres against the Highlanders on Saturday night, which would give the Brumbies their most inexperienced backline of all time.

The dual blow means Fisher, already without George Gregan and Stephen Larkham, is without his most senior quartet of backs - Mortlock, Ashley-Cooper, Fairbanks and Clyde Rathbone - for their opening home game.

Smith is the likely candidate to wear the unlucky No.13 jersey and Mortlock said the former English Super League player was making progress in his transition from league.

"He's got a bit of class about him but obviously when you're playing in the centres ... coming from league there's a lot to learn," Mortlock said.

"He's been very diligent in learning as much as he can.

"The reality of it is when you're a centre in union you're directing a lot of multi-phase stuff.

"You're the eyes and hopefully communicating with the team as much as possible."

Fisher is hoping to bolster his forward pack with Wallabies lock Mark Chisholm (groin) and ex-Queenslander Mitch Chapman (back) in line to return.

Chapman would make his Brumbies debut after missing the loss to the Crusaders.

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