Halfback Josh Valentine will shrug off a niggling hamstring problem to try and fix the Brumbies' attack woes in Saturday night's Super 14 grudge match with NSW.

On a day the Waratahs named both Benn Robinson and Tatafu Polota-Nau in an extended 25-man squad, Valentine declared himself fit to play at ANZ Stadium.

The five-Test halfback has missed the Brumbies' last two matches due to a hamstring strain and suffered another twinge at training on Tuesday but is set to be named in place of Patrick Phibbs when the team is named on Thursday.

"The signs are good," Valentine told AAP.

But the news is not so good for former Wallabies skipper Stirling Mortlock, who continues to have problems with his back injury and will be replaced by Andrew Smith.

The 104kg Smith will make his run-on debut at outside centre with Wallabies fullback Adam Ashley-Cooper moving back to the wing.

Brumbies coach Andy Friend is searching for a solution to his team's frustrating inability to get over the advantage line in the 23-12 loss to the Hurricanes last Friday.

The defeat left the sixth-placed Brumbies (26) precariously placed, four points outside the top four and desperately needing to beat fifth-placed NSW (29).

Valentine felt his well-tuned halves combination with former Force teammate Matt Giteau could help address their lack of depth in attack.

"We seemed to be playing well behind the advantage line and passing it back and passing it back further and getting caught," he said.

"Coming off three games at inside centre and (five-eighth Giteau's) mindset could have seen him sit a bit deeper.

"Hopefully with some good go-forward ball we can flatten right up and have a real good crack with our backline."

Valentine is one of six Brumbies who have played for the Waratahs at Super 14 level, along with Rocky Elsom, Huia Edmonds, Ben Hand, Stephen Hoiles and Alfi Mafi.

Elsom has underlined the challenge by rating NSW a more complete team now than when he played for them in the 2005 and 2008 finals losses to the Crusaders.

"The way their backs have been playing has really helped their game," Elsom said.

"That's probably a big reason why they've got a lot more bonus points than us."

NSW will wait until Friday to decide on the fitness of Polota-Nau (shoulder) and Robinson (forearm).

But coach Chris Hickey said hooker Polota-Nau would train on Thursday and indicated he was looking like a solid hope of starting, even though Adam Freier has been called into the squad on standby.

Robinson is in more doubt and Sekope Kepu will start at loose-head prop if he is ruled out.

Hickey is hopeful Rob Horne will play after straining his right buttock muscle.

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