Injury-plagued world champions South Africa have postponed until Thursday the announcement of the team to face Australia in the Tri-Nations this weekend. Coach Peter de Villiers planned to reveal his Springbok side Tuesday afternoon but changed his mind because of doubts concerning back-row forwards Pierre Spies and Danie Rossouw. Number eight Spies is battling to recover from a months-old groin injury and Northern Bulls team-mate Rossouw has been on a drip for several days to combat severe gastroenteritis. If fit, both are set to face the Wallabies Saturday at Kings Park with Heinrich Brussow, who has spent much of the past 18 months sidelined by various injuries, completing the back row. Ashley Johnson and Ryan Kankowski, who can play flank or number eight, were called up Monday as cover and there has been media speculation here that Willem Alberts could also be considered despite not being in the 27-strong squad. South Africa, who suffered heavy losses in Australia and New Zealand last month after 21 mainly first-choice players could not travel because of injuries, have been particularly hard hit by back-row problems. Schalk Burger and Juan Smith are training with the Springboks but have been ruled out of the Kings Park showdown and hopes of long-term casualty Duane Vermeulen being available for World Cup selection are dwindling. Only two of the team outclassed 40-7 by the All Blacks in Wellington late last month -- skipper and hooker John Smit and number eight Rossouw -- are expected to start against Australia. A new backline would see Francois Steyn at full-back, JP Pietersen and Bryan Habana on the wings, Jaque Fourie and Jean de Villiers in the centre postions, Butch James playing fly-half and Fourie du Preez at scrum-half. All bar injured De Villiers started in the 15-6 Rugby World Cup final victory over England in Paris four years ago although Steyn was a centre then with now retired Percy Montgomery the full-back. After playing with rookie props Dean Greyling and Werner Kruger in Australasia, 104-cap Smit is likely to have much more experienced support this weekend in the shape of loosehead Tendai 'Beast' Mtawarira and tighthead Jannie du Plessis. The long-serving lock partnership of Bakkies Botha and Victor Matfield is set to resume active service while, fitness permitting, Brussow, Rossouw and Spies form the loose trio. South Africa complete their Tri-Nations schedule on August 20 against the New Zealand All Blacks in Port Elizabeth and launch the defence of the world title against Wales on September 11 in Wellington.