I knew I'd done something as soon as I heard the cracks
Australia's stand-in captain Will Genia is expected to be sidelined for up to six months after rupturing the anterior cruciate ligament in his right knee.
The injury, which happened late in the Wallabies' 26-19 win over South Africa in a Rugby Championship match at the weekend, follows that of regular captain James Horwill (hamstring) and the man who replaced him, David Pocock (knee), who were both already ruled out for the remainder of the series.
Genia, who underwent scans on Sunday at a Perth hospital, will be replaced for the Australia match against Argentina on the Gold Coast next Saturday by veteran halfback Brett Sheehan.
The 24-year-old Genia is unlikely to return to action until the start of next year's Super Rugby season.
He said: "I took the high ball, it twisted and I heard a few cracks."
"I knew I'd done something as soon as I heard the cracks and then when I got up and tried to take off and couldn't support any weight I knew I'd done something quite serious."
Nathan Sharpe is expected to be handed the captaincy for the game against the Pumas on the Gold Coast this coming Saturday.
When Genia hobbled from Patersons Stadium in Perth, with a heavy ice pack strapped to his knee, Pocock said to him: "Mate, let's not have a captain."
The leadership and depth of the Wallabies will now be severely tested for the remainder of the year with Sharpe retiring after the Rugby Championship, and Horwill and Pocock only outside chances of travelling to Europe in November.
The Wallabies say they're up to the character test that will come with losing a player as influential as Genia.
Genia is confident there's enough experience in the group to cope without a third elected skipper.
"Sharpie assumes that leadership role and what last night and over the last couple of weeks has showed is we're building depth," he said.
"I reckon [Phipps] will do really well. He's got a good work ethic and he's got a big motor."
Deans, who has received some relief from the pressure mounting on his job, said the tenacious game of Sheehan will benefit the group and is confident Phipps will cope despite his lack of Test experience.
"Phippsy's ready. It's been a challenge for him to be in the shadow ... but he's understood the need for him to really immerse himself in training as though it's the game," said Deans.
Lock Sitaleki Timani (hamstring) is highly unlikely for the Argentina fixture, with Rob Simmons or Kane Douglas to replace him.
Veteran hooker Stephen Moore succumbed to a low grade hamstring injury before the Springboks match, while centre Rob Horne tore his hamstring in club rugby.
The positives for the Wallabies are that inside centre Pat McCabe is available for selection against the Pumas and James O'Connor will join the squad with a view to being fit for the trip to South Africa and Argentina later this month.
Wing Drew Mitchell has also managed to avoid needing further surgery on his troublesome leg injury and will return to full training.