The Lions were labelled "slabs of red meat" by one Australian newspaper when Warren Gatland's squad was announced and have lived up to that billing with some bruising displays of forward power in their tour matches.
The Wallabies expect more of the same at Lang Park on Saturday, especially in the first 20 minutes of the match, but promised to fight fire with fire.
"It's going to be critical," lock Horwill said. "We understand that the Lions play a very physical brand of football. They've been very physical, very confrontational.
"And that's the way they've played a lot of their rugby. It's a big job for the guys up front to make sure we not only match that, but we take the ascendancy there."
Horwill, nicknamed "Big Kev" for his infectious enthusiasm after a famous Australian television advert, thought the first Test would be close but that Australia would win.
"It's going to come down to a number of things," he added.
"The main thing, you've got to make sure you work hard. Games of this magnitude, there's not a lot in it from player to player.
"Everyone across both teams is incredibly skilful. It'll come down to the workrate. There's never a lot in these sort of games. The margins are going to be very small."
On Saturday, Horwill will renew an acquaintance in the second row with Paul O'Connell, who had an inspired game at Eden Park when Ireland smashed Australia up front to record a big upset at the 2011 World Cup.
That is probably a match Horwill would like to forget but he said the Wallabies were well aware of how well the 2009 Lions tour captain had been playing despite missing most of the season through injury.
"He's a guy who has played a number of Tests for Ireland, and been on Lions tours," Horwill said.
"He's a guy we're certainly wary of his capabilities across the ground, at the lineout and obviously the breakdown he's been very influential. He's come back a little bit rejuvenated."
Experienced Wallabies hooker Stephen Moore was much missed in the World Cup clash against Ireland two years ago after being forced to pull out of the team on the morning of the match.
The 30-year-old, who modelled his game on that of Ireland and Lions rake Keith Wood, said the selection of loosehead prop Alex Corbisiero instead of his England team mate Mako Vunipola was a clear statement by the Lions.
"I thought Vunipola had been very good for them, so he can consider himself unlucky," he said.
"I think they've been pretty clear they've picked a scrummaging front row, and that's the way they intend to play. As far as that goes, that's why Corbisiero is there obviously."
Scrum-half Will Genia probably still has nightmares about being picked up and carried backwards by the Irish loose forwards in the Eden Park match in 2011 and would not like to see a repeat on Saturday.
Openside flanker David Pocock was another late withdrawal from that match and is again unavailable for the Lions series because of a knee injury.
While he will undoubtedly be missed by Australia, Genia said he thought the two opensides in the matchday squad for Saturday could have a major influence on how the forward battle goes.
"I think it's a massive strength for us," he said.
"We've got exceptional players like Michael Hooper, who'll do a great job for us, and then to have the luxury of someone like Liam Gill who can come on when it gets loose.
"He's great at the breakdown, he's great at pilfering. He's just got a really good all round game.
"When the game does get a little bit loose ... he's got the ability to play with the ball in hand, and carry, and also get stuck into the tight stuff. We're very fortunate to have those two guys in the group."