The Wallabies team will not be announced until Thursday but a spokesman said the hulking forward, who normally plays at number eight or blindside flanker, would be in the 23-man squad for the match at Sydney's Olympic stadium.
"It's a very big occasion, everyone will be watching in Australia and around the world and it's one I'm very much looking forward to," said the 25-year-old Western Force forward.
"I'm very excited, it'll be my first game since Wales 2011. Having missed last year with a few injuries, I'm very excited to be back."
McCalman, who can also cover second row, was called into the preliminary squad for the series after loose forward Scott Higginbotham dislocated his shoulder in a Super Rugby match.
His inclusion in the squad, most likely on the bench, indicates some changes in the forwards even if number eight Wycliff Palu, blindside Ben Mowen and openside Michael Cooper are expected to start for a third successive Test.
The Wallabies have reported no injuries so it may be that coach Robbie Deans is just bringing some extra muscle onto the bench, perhaps at the expense of a backline player, for what is expected to be another bruising forwards battle.
"I think the last two games have shown that it's going to be a forwards orientated game," said McCalman.
"But it's very important for the backs to be strong at the breakdown as well."
The Lions had great success with the rolling maul early in the second Test last weekend and that is the sort of threat that McCalman's physicality would help neutralise.
"They obviously see themselves having a strong maul and view that as not our strongest area but we feel that is a very strong area for us," he said.
"We'll just have to adapt our game a bit, we'll have to wait and see."
McCalman won the first of his 21 caps against South Africa in 2010 and played in all seven of Australia's matches at the 2011 World Cup before a broken shoulder and a broken wrist wrecked last season for him.
Having played a semi-final against hosts and eventual champions New Zealand at the last World Cup, McCalman knows all about big matches but thinks Saturday will pip even that experience.
"That was certainly a big game but I think this will be bigger," he said.
"Once every 12 years, the deciding match in Sydney in front of 80,000 people, certainly the biggest game, yeah."
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