Halfback Finlay Christie said the Waratahs were more physical and better drilled with a good pack.
"They're going to come at our breakdown pretty hard. We've had to look at that and they're not going to roll over. We're going over there expecting a big tussle."
Christie said the game was also a good one for the Blues to see how they respond to an early-season loss like the one they suffered to the Hurricanes at the weekend.
"We probably lost the physical battle up front, and that's not something we take lightly. We've had a good, hard look at ourselves over the last couple of days and made a few fixes.
"When we looked at our review and what we created, we created a lot of opportunities, especially in that first half. But we had 18 turnovers in the game. The first four times we got into their 22, we lost the ball, so you can't expect to score many points when you have stats like that."
They need to finish the chances they create to have a chance of beating the Waratahs.
The Waratahs have been playing well, beating the Crusaders and just losing to the Highlanders.
"We've got to be ready. They've got some athletes in the backline and a big physical pack. They've got great loose forwards and some big locks. They love to stack tackle and try to hold our guys up and make a real mess at the breakdown.
"That's somewhere we've got pride in ourselves. We had a good training today, so we're looking forward to it. It's going to be a pretty good test."