To see the Socceroos train overnight...

While Kewell, whose much-talked about groin injury has dominated Australia's build-up to the 2010 World Cup, was able to join in an intense two-hour training session here on Tuesday night while Cahill was a spectator.

Cahill is still recovering from a neck injury sustained during the first half of Saturday's 3-1 loss in a warm-up match against the United States and while the rest of Pim Verbeek's squad engaged in a full-scale practice match, the Everton star was having shooting practice alone on the side of the pitch.

The sight of Cahill - by far Australia's most prolific scorer in recent years and the man considered most likely to supply the goals for a team that has struggled to score consistently under Verbeek - being unable to join in training just five days out from the Socceroos' opening game is a major concern.

With 20 goals from just 40 appearances, Cahill has scored more goals than any other member of the Australian squad and famously scored Australia's first ever goal at the World Cup finals four years ago when his two late strikes against Japan secured the memorable come-from-behind 3-1 victory in the opening game in Germany.

Cahill was listed as one of the Socceroos' players to face a growing Australian media contingent before training at St Stithians College in Johannesburg on Tuesday night but elected not to speak to any members of the print media where he would have faced intense questioning about his fitness.

But while there is now some doubt over Cahill for the opening game in Durban on Sunday, Kewell seems to have won his fitness battle just as Verbeek predicted.

The 31-year-old - whose late goal against Croatia four years ago secured Australia's passage to the knockout stages of the World Cup for the first time - trained strongly on Tuesday night and looks set to be ready to face Germany.

Kewell has missed both of Australia's warm-up games against Denmark and the USA but appears to have timed his return to fitness to perfection.

Australia's other big injury concern in veteran midfielder Brett Emerton also joined in full training and also looks to have overcome his recent calf problem.

The Socceroos looked sharp while training in the cool evening conditions of Johannesburg but again had trouble at times with the controversial World Cup ball which moves dramatically at altitude, particularly at night when the temperature begins to drop.

At one stage a hopeful long range shot from youngster Tommy Oar swerved sharply in the air at the last minute and went straight through the hands of third goalkeeper Eugene Galekovic and into the net to give the Socceroos and their three goalkeepers especially in Mark Schwarzer, Adam Federici and Galekovic a reminder that even tame shots from distance could be hard to save at this World Cup.

To see the Socceroos train overnight...