The Force finished third-last in the competition last year but have won the past four of their six games this season to occupy fifth spot among the all-important top six qualifiers on the Super Rugby ladder.

Waratahs coach Michael Cheika said the Force would have placed expectations on themselves to win a fifth-straight match this weekend. But Foley said that was a way off being considered favourites.

"We're realistic, we've had a nice start to the season, we've won four games," he said of the club milestone.

"But last year we won four games and drew one, so we still haven't bettered that. If we get past last year then we start to chase some of the things we're aspiring to this year. But we're pretty realistic about it."

The Waratahs sit one spot and two points ahead of the Force on the ladder and are, despite Cheika's protestations, the bookies' favourites to win the match.

Both sides have been hit by injuries in both forwards and backs during the past fortnight and will not name their teams until Thursday.

The Waratahs lost their two starting wingers as well as No. 8 Wycliff Palu but will welcome back fullback Israel Folau and Rob Horne, who was suspended.

The Force will be without in-form centre Junior Rasolea, but have a strong candidate in line for the No. 13 jersey in South African Marcel Brache, with Kyle Godwin expected to stay at inside centre.

They are also still without breakaway Chris Alcock and second-rower Hugh McMeniman, but have notched their recent wins in spite of changing personnel up front.

Foley was amused when he heard Cheika had cast the Waratahs as underdogs leading into the match, with the Perth side boasting a fraction of their rivals' Test-capped players.

"What we have done well to date is eliminate any of that noise that is subjective," he said.

"We know what we did last week objectively but the sense of where you stand going into a game and whether it means you're a favourite or an underdog, is just irrelevant. We just want to be better than we were last week."

Foley also rejected speculation the Force had the edge over the Waratahs' Wallaby-studded pack, despite competition statistics putting NSW four or five places behind their western cousins in both line out and scrum success.

"Maybe they haven't scrummed as well as they [could] have, but I'm in a pretty good position to know what they're capable of," Foley said, referring to the three seasons he spent as assistant NSW coach and one season he spent as head coach.

"We're up against an international forward pack, particularly a Wallaby front row, so this will be a big challenge for us. I still think we have 10 or 20 per cent improvement in us in our scrum."