Dave Rennie backs Michael Hooper after his withdrawal ahead of Argentina game

Australia head coach Dave Rennie has come in support of Michael Hooper after the Wallabies captain pulled out of the Rugby Championship opener against Argentina due to personal reasons.

Hooper was set to lead the side for the Saturday's encounter Mendoza but withdrew himself from the clash on Friday as he admitted that he was not on the right mindset.

Reacting to the news, Rennie said the team management did not see any indication from Hooper but appreciated his honesty on the situation.

“Nothing that was evident to us, how he trained and contributed around the team and leadership was excellent and clearly he’s been struggling and masking that well,” he told reporters.

“It came to a head last night and he was brave enough to call Sharon (Flahive, Wallabies team doctor) and have a chat with her and then involved (team manager) Chris Webb and myself to get an understanding of where he is at…obviously he’s felt he can suppress things over the past handful of weeks so we certainly weren’t aware of things.

“He’s such a professional, he was able to get on and do his job. He addressed the team today which took enormous courage to let them know he’s not ok and felt it was best for himself and the team that he heads home.

“It was an easy decision to let him go home and he’ll get plenty of support around him.”

Hooper will now accompany Dave Porecki on the flight to Australia with the latter ruled out due to a head injury. In Hooper's absence, James Slipper has been handed the captaincy while Fraser McReight comes at number seven.

"It's not uncommon in life is it?" Rennie said of Hooper's issues. "(Rugby's) a cross-section of society. Often men will say bugger all and suffer in silence.

"It took a lot of courage from him to address the group, so a huge amount of respect from everyone and respect that we want to get him home and get as much support around him as we can."