Australia have been hit with a double injury blow two weeks out from their opening Rugby Championship match against the All Blacks in Sydney, losing prop Laurie Weeks and winger Joe Tomane.
Prop Paddy Ryan and uncapped Melbourne Rebels wing Tom English have been called into the squad as replacements.
Both Weeks and Tomane have hamstring injuries and are expected to be sidelined for two to three weeks.
"As it is with sport, injuries provide an opportunity for other guys to come through, and I'm sure Paddy and Tom are both excited about taking part in our preparations for the All Blacks," McKenzie said.
Ryan – who has won three caps - and English have both had exposure to the national program this year, with Ryan playing in Australia's victory over France in Melbourne in June, while English was part of the Wallabies training squad.
"It's no secret we're trying to build more depth at tighthead prop and the upcoming fortnight will be a good chance for Paddy to continue improving at this level," McKenzie said.
"Tom is a guy we are continually learning more about and is someone who impressed us with his attitude and abilities at training during the June series, along with being a consistent performer for the Rebels throughout the year."