The NSW Waratahs suspect the Lions are playing selection tricks in a desperate bid to climb off the bottom of the Super 14 ladder.

NSW coach Ewen McKenzie on Friday said the Waratahs were wary of walking into an ambush at the Sydney Football Stadium on Saturday night after the South Africans sent a mid-week SOS for classy back Earl Rose and crafty lock Cobus Varkhond Grobler.

The seasoned duo have been drafted in following injuries to Justin St Jerry (concussion) and Anton van Zyl (calf) and McKenzie said his high-flying Waratahs were on guard heading into what shapes as a real danger game.

"We don't necessarily think the team they've named is the team that's going to play," McKenzie said.

"Cobus Grobler and Earle Rose have come across, so I doubt they'd come across if they weren't going to include them in the (squad of) 22.

"We expect them to have a more experienced team than they've named so we're preparing for a pretty big game."

The Lions are stone motherless last and are widely expected to prove fodder for the Waratahs, who are undefeated at home this season and chasing a fourth straight win to cement a place in the top four.

McKenzie, though, said it would be stupid to take the Lions lightly.

"We've been at that end of the comp so we know what it looks like," he said.

"We understand that you can be there but not be actually be far away from the action, and we saw that last week against the Crusaders - they pushed them there and they were leading at halftime."

McKenzie predicted the proud Lions would be doing everything in their power to finish above as many South African teams as possible, and wouldn't be lying down on Saturday night.

"Just knowing a bit about them, they've got season goals and I think they still believe they can achieve those goals in terms of where they finish," he said.

"Obviously winning is part of that process. It's not a nice feeling when you lose back-to-back, particularly when you get close.

"So they'll feel at some point that, if they can get a bit of luck, the wheel will turn for them."

A big victory over the Lions and then success against the Sharks in their final home game next week would leave the Waratahs on track for an all-important top-two finals berth.

Yet both McKenzie and skipper Phil Waugh, as they have all season, maintained nabbing a precious bonus point for scoring four tries or more was not a priority.

"I've never spoken about bonus points," McKenzie said.

"We set up the game to make sure we win it and then, if an opportunity comes along, well obviously we'll be endeavouring to do that as well.

"But that's a consequence of playing well, so we'll just concentrate on playing well."

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