Powerful Wallabies utility Adam Ashley-Cooper will be given until the last minute to prove his fitness for the Brumbies' must-win Super 14 clash with the unbeaten Sharks on Saturday night.

Ashley-Cooper sat out training for the second successive session on Friday with a painful back problem that has plagued the tackle-shedding back for the last two weeks.

With skipper Stirling Mortlock (head knock) already ruled out, Ashley-Cooper's presence at outside centre is crucial to the injury-riddled Brumbies' hopes of upsetting the Durban-based outfit.

The 24-year-old has boldly declared himself a certain starter and coach Laurie Fisher is confident he will play but much depends how his back pulls up on Saturday.

Ashley-Cooper has been suffering from spasms where his ribs connect to his backbone since a tackle went wrong during the loss to the Chiefs two weeks ago.

Fisher, who has put reserve Leo Afeaki on standby to play No.13, indicated he was prepared to wait until kick-off for Ashley-Cooper to come up.

"He's not 100 per cent but he's well on in the improvement, so we're not going to run him today," the coach said.

"He'll just rest up and recover and at this stage he's in no doubt for tomorrow.

"The doctor is confident and he said he was significantly better than he was yesterday but there was no benefit in running him there today.

"We've got seven players unavailable for selection at this stage so we don't need any more. That will do."

Fisher denied the events of the week - with the Brumbies board replacing him with Andy Friend after this season - had affected preparations for what looms as a play-off match for his ninth-placed side.

"I don't think it should be an excuse and no one will be using it as one," he said.

"We've trained well, the mindset is very good. It has been a very positive week for us in terms of motivation."

Although he winced as he said it, stand-in skipper George Smith hoped the Brumbies could take a leaf out of the book of arch-rivals NSW.

"A good example is the Waratahs. I don't like to talk them up all the time, but they definitely came out when Ewen McKenzie was passed over (as coach) and have played well in their two games (since)," he said.

The Brumbies do have form over the Sharks at home beating them in their last five matches in Canberra, including the 2001 Super 12 final.

The closest any team has gone to beating Dick Muir's men this year was the Hurricanes a fortnight ago when they held them to a 17-all draw and had a seemingly-legitimate try disallowed on full-time.

Muir has shuffled his backline with French maestro Frederic Michalak playing five-eighth and classy Springboks youngster Frans Steyn moving to outside centre.

Fisher stressed precision in attack needed to improve markedly from that on show in the 16-11 upset of the Blues.

"Consistency is our key," he said.

"We probably need to try and bring the same abrasiveness to the game that we did last week.

"We need to execute when we get given opportunities. Playing against a side that's undefeated if you get three or four try-scoring opportunities you have to take them.

"I don't think they will let us off as lightly as the Blues did last week."

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