O'Connor had been expected to miss the June 5 international with the Scots but had hoped to be back in time for at least part of the three-match series with Wales that begins on June 9.
"Disappointing result - liver healing very nicely, just going to run out of time...if only I had a couple more weeks up my sleeve," O'Connor tweeted after it was revealed that he will have further scans in a month's time to see when he can play again.
The news is a major blow for Australia head coach Robbie Deans who was mulling over playing O'Connor at fly-half a year out from the 2013 Lions tour.
With regular starter Quade Cooper only having returned from a seven-month absence due to a serious knee injury last weekend, Deans had been considering handing O'Connor the No10 shirt after the youngster had requested the chance to be closer to the action.
O'Connor has played most of his Test rugby at wing or full back but was being looked as a fly-half and centre as well as for his usual back-three berth.
But with the Rebels' medical team stating that O'Connor must wait a further four weeks before returning to contact training, Deans will have to look elsewhere for inspiration this summer.
O'Connor's absence increases the likelihood of a return to Test action for Cooper, who tore his anterior cruciate ligament during the Bronze Medal win over Wales in the 2011 World Cup, but Deans could also be tempted to move Kurtley Beale up from full back.
Beale has been one of his country's standout performers over the past three seasons but injury to O'Connor and the departure of former England fly-half Danny Cipriani has forced the Rebels to move him to 10 in recent weeks.
The ex-Waratah has excelled in the playmaking position and could now be a serious option there for the Wallabies if Cooper is deemed not to be ready for Test match rugby and if Deans would prefer to play the more pragmatic Berrick Barnes at inside centre.