Australia back James O'Connor has suffered a fresh injury blow after tearing a hamstring during the Rebels' Super Rugby defeat to the Reds on Friday.
The 21-year-old had only just returned to action after more than a month out with liver and hamstring injuries.
O'Connor now faces another two months on the sidelines and will miss the Rebels' last two matches of the season in South Africa.
He is also rated doubtful for Australia's first match of the inaugural Rugby Championship against world champions New Zealand in Sydney on 18 August.
Melbourne's versatile back Kurtley Beale could also miss the flight to South Africa after taking a knock against the Reds.
He will be assessed by medical staff on Tuesday before a decision is made.