The desperate NSW Waratahs are hopeful inspirational hooker Tatafu Polota-Nau can shrug off his battering in Canberra in time to line up for their must-win Super Rugby clash with the Bulls.

A dazed Polota-Nau was replaced before halftime in Saturday night's 23-6 loss to the Brumbies in Canberra after a sickening collision with Wallabies teammate Pat McCabe.

The 31-Test hooker had already been down earlier in the match before copping a heavy head knock when he fell into McCabe's tackle, putting him in doubt for Friday night's home match against the in-form and highly-physical South Africans.

Waratahs coach Michael Foley told AAP on Sunday the Wallabies hooker should be right to bounce back but will be assessed early in what is a short six-day preparation.

Polota-Nau was sorely missed in the second half with replacement John Ulugia struggling with his lineout throwing as the Waratahs battled to stay in the contest with the impressive Brumbies.

Foley admitted time was fast running out for the Waratahs to make the finals after falling nine points adrift of the Brumbies (35) in the Australian conference.

Although they had much to play for, the Waratahs wasted a promising start as they were outpointed by the hungry Brumbies forwards at the breakdown and failed to score a try.

"The Brumbies are two wins ahead of us now and clearly that's a fair bit of ground to make up," he said. "We don't have much time to make it up.

"The Brumbies are definitely in control of their own destiny. All we can do is focus on the things we have control of."

The Waratahs have an ominous schedule looming, starting with the second-placed Bulls, before heading to South Africa to play the Stormers and the Cheetahs.

Against the Brumbies, Foley said his squad had squandered their chances when they dominated possession for the first half, running the ball and looking dangerous in the Brumbies' 22.

"We'd got past half of their team to two-thirds of their team and there was a few defenders left to beat and we'd throw a loose pass," Foley said.

"When you build pressure after five or six phases and you're about to do the job - you've just got to do that."

The Waratahs also paid for key defensive lapses, no more obvious than when winger Henry Speight, with hardly a metre to work in, evaded Berrick Barnes and two other would-be tacklers for the Brumbies' first try, while Andrew Smith brushed past Adam Ashley-Cooper and Atieli Pakalani for their second.

"If you don't make your tackles, people are going to score tries," a disappointed Foley said.