The Waratahs struggling season looks set to suffer another blow as hooker Tatafu Polota-Nau will miss the clash against the Stormers in Cape Town.

The Waratahs are expected to announce Polota-Nau's withdrawal officially before the match but Michael Foley told AAP he wasn't prepared to risk the Wallabies hooker who is still suffering from two nasty head knocks against the Brumbies in Rd. 11.

Coach Foley says that Polota-Nau is close to making a full recovery but that it was not worth taking a risk in playing the 26-year-old even in such an important match.

The Waratahs are expecting a hugely physical clash but need to win the match as another loss will realistically end their play-off hopes.

The Waratahs have only won one match in 13 overseas and have not won on foreign soil in two years.

John Ulugia was bracketed with Polota-Nau so he should start at No.2 this weekend with the Wallabies hooker making a return against the Cheetahs.

"I think he'll only miss (the Stormers match) by a day," Foley told AAP from Cape Town.

"We're so close but playing could be a risk to him and we don't want to take that risk.

"People have played with corks and sprains and all sorts of things before but I think it's just so unwise to put people at risk who have had a head knock and they're not 100 per cent right."

Foley says that he has looked closely at how the Reds and Crusaders beat the Stormers last season in Cape Town and will aim to play a disciplined and strategic field-position game.

Foley said that the trick to beating the Stormers would be choosing when it was best to attack as unlocking their defence is extremely difficult.

"Stats would tell you that over the last two or three years that the better attacking sides have actually lost to them when the defence is set," he said.