Dennis, capped 15 times for Australia and belatedly released from the Wallabies' training camp, said the tackle area would ultimately be decisive in the game at Sydney Football Stadium, but the Waratahs would also hope to leave the tourists drained.
"The breakdown is going to be key. That's something we've really worked on," the versatile forward told reporters on Friday.
"I'm not saying we've got an edge there, but we're going to have a real crack at the breakdown.
"And I think just the way we attack with the ball in hand, that's something we're building as a group and we're going to look to really have a go at them with the ball in hand... obviously run them around a bit.
"It's a tough tour. They've got 10 games on the tour and they've played a few already and it still hasn't come up to a test match.
"Another physical encounter tomorrow night helps the Wallabies cause and gives them an opportunity to see a few areas where they might be able to expose them in that first test."
The Lions have been undefeated in their three tour matches Down Under, but were pushed all the way by the Quade Cooper-captained Queensland Reds in their 22-12 win at Lang Park last Saturday.
The Waratahs, shorn of eight Wallabies players training at a national camp in Queensland, lack the attacking firepower and pace of the Reds, but are unlikely to lack application in their last match before a two-week break in the Super Rugby season.
"It's a two-horse race. It's not as if we're not in with a chance," said Dennis, who will line up at number eight against the Lions. "We're very much going out to win the match and to really represent the state with pride.
"Anything can happen. We're going to give it everything we've got. We've got a couple of weeks off afterwards so there'll be nothing left in the tank."
While the Lions braintrust were thankful to the Ewen McKenzie-coached Reds for handing the tourists a first genuine contest on tour, coach Warren Gatland and his assistants are unlikely to be surprised by another up-tempo match.
Forwards coach Graham Rowntree virtually invited the Waratahs to follow the Reds' model after talking up the Queensland team's performance.
"The Reds was a great workout on many fronts and, speaking to the lads about it, they were pretty worn out," Rowntree told reporters.
"A lot of guys were cramping up and you don't see that in test rugby these days.
"The ball-in-play time was ridiculous. They kept us moving around and they brought a real intensity to the breakdown.
"So if the Waratahs were watching that, there's a blueprint there for how to try and beat us tomorrow."