The injury focus has shifted from one star Socceroo to another after Tim Cahill failed to train fully just five days out from Australia's World Cup opener against Germany.

As Harry Kewell and Brett Emerton returned to full training, Cahill completed just the warm-up and light work at the session in Johannesburg on Tuesday night before sitting out the practice match which followed.

Cahill injured his neck in Australia's 3-1 friendly loss to the United States on Saturday and was taken to hospital for observation.

Socceroos coach Pim Verbeek said scans had shown no serious injury.

But the Everton midfielder is yet to train fully since that match.

Cahill also brushed off media questioning about the extent of his injury prior to training.

While his teammates played the practice match, he was reduced to shooting for goal and light jogging.

"I'm fine," was all Cahill offered when asked about his fitness.

Cahill is without doubt Australia's most important strike weapon going into the match.

His knack for scoring important goals from midfield at a rate of one every two games for his country is something the Socceroos cannot afford to be without against one of the tournament favourites.

Germany defender Per Mertesacker admitted Cahill is top of his side's hit-list as they attempt to limit his impact in Sunday's match in Durban.

"Tim Cahill has enormous experience and has grown tremendously in England, he is one of Australia's most dangerous players and will be their midfield maestro," Mertesacker told reporters on Tuesday.

"But if we can mark him tightly, it will make it hard for him to play a role."

Emerton, who has been battling a calf injury, and groin concern Kewell both trained well.

Kewell looked particularly sharp and scored a well-struck goal during the game.

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