Australia midfielder Vince Grella sprained his knee at training and is out of the World Cup Group D encounter against Ghana in Rustenburg, but is expected to be available to face Serbia.

The 30-year-old failed to finish Australia's training session on Wednesday. With a closed training session on Thursday for the Socceroos, it is yet unknown who coach Pim Verbeek will call-up as a replacement for the one-time untouchable midfield linchpin.

Grella was substituted at half-time of the 4-0 loss to Germany in Durban, with his place in Australia's starting XI for this weekend's game in jeopardy - after a string of relatively poor performances.

With Tim Cahill suspended, under-fire boss Verbeek is certain to make at least two changes from the side that took the pitch in the comprehensive loss to Germany.

Grella, a veteran of 46 internationals, recently had a proposed move from Blackburn Rovers to Galatasaray called off as his career lurches from one frustrating injury to another.