Sydney - Australia's Test team left for their South African cricket tour on Wednesday with captain Michael Clarke concerned over two players forced to remain behind to receive treatment on their injuries.
While fast bowler James Faulkner was ruled out of the tour on Tuesday with a right knee injury, Shaun Marsh (calf soreness) and Jackson Bird (back) will have to prove their fitness before making the trip.
"I'd like them to be on this plane now but that's not realistic," Clarke said at Sydney airport.
Both would likely need to leave Australia by the weekend if they want to take part in Australia's one warm-up match in Potchefstroom from February 5-8.
The first Test at Centurion begins on February 12. The second Test will be played in Port Elizabeth from February 20 and the third in Cape Town from March 1, followed by three Twenty20 matches.
Bird bowled well in the nets on Tuesday and will be passed fit if he has another positive session. Marsh's calf muscle strain is said to be minor, but medical staff are treating the injury with caution because he has had similar injuries before.
Clarke said Australia, who completed a 5-0 Ashes sweep and a 4-1 win in the one-day international series against England, need to back that up against the world's No 1 Test team in South Africa.
"A lot of teams in Test cricket are having success in their own back yard, but the greatest challenge is to be able to win away from home," Clarke said. "That's what we face right now."