Socceroos coach Ange Postecoglou departs for Brazil on Wednesday with doubts on key players and admitting a tough training regime could decide who survives his final World Cup cut.

Postecoglou released three players - injured defender Curtis Good and midfielders Adam Sarota and Josh Brillante - on Tuesday, leaving a travelling squad of 27 which must be reduced to a final 23 on June 2.

The coach insisted he hadn't yet decided on the unlucky last four to be omitted.

"To say that I have got 23 in my mind - no, I don't, because at this point we need all 27," said Postecoglou.

"We're going to be working the players pretty hard so you just don't know how people are going to cope."

Postecoglou's chief concern is new captain Mile Jedinak, recovering from a groin strain and uncertain when he'll play again.

Jedinak hopes to play in Australia's warm-up game against Croatia on June 6, one week before their World Cup opener against Chile.

"We're all confident that will happen but it's still a little while away," Jedinak told reporters in Sydney on Tuesday.

Defender Ivan Franjic will travel to Brazil with Postecoglou, easing concern over a knock to the left knee which forced the Brisbane Roar stalwart from the field in Monday's 1-1 draw with South Africa in Sydney.

Another defender, Matthew Spiranovic, missed the drawn friendly with an ankle complaint.

Midfield ace Mark Bresciano also didn't play against the South Africans, rested as a precaution after complaining of back stiffness after training.

Playmaker Tom Rogic, battling a groin complaint, was also missing.

But Postecoglou made no apologies for a brutal 10-day training camp leading the drawn friendly against South Africa.

"I would be very, very surprised if other countries aren't doing a similar thing," he said.

"We're not flogging the players. We're trying to make sure that when the first game comes around, they're in great condition."

Postecoglou said that the decisions to cut Good, Sarota and Brillante were difficult.

"Obviously players being so close to getting on the plane to a World Cup and being part of it, it's not the best news to deliver," he said.

Good failed to overcome a nagging hip injury while Postecoglou wasn't convinced midfielder Sarota, despite recovering from a knee reconstruction, could handle the rigours of a World Cup.

A-Leaguer Brillante fell victim to the Socceroos' midfield depth, Postecoglou said. AAP