A potential danger team in Australia's World Cup group emerged even further out of the shadows last night. Central European nation Serbia, ranked 15th in the world, sent a real warning to the Socceroos when their second-string team disposed of Australia's Asian rivals Japan 3-0 away from home.

Serbia were without regular starters Nemanja Vidic, Dejan Stankovic, Marko Pantelic, Nikola Zigic, Milos Krasic, Nenad Milijas, Branislav Ivanovic and Vladimir Stojkovic and although Japan were not at full strength, they were only really without European-based stars Keisuke Honda and Takayuki Morimoto.

This result, produced by a group of Serbian players who will not start in the World Cup, must have the Socceroos, as well as Germany and Ghana, very wary of what they are really capable of.

It has added real spice to what was already a tough Group D and has given Australian coach Pim Verbeek something extra to think about as a handful of his key players strive to get to full fitness before June.

Meanwhile, Serbia coach Radomir Antic, was extremely pleased with his side's performance which bodes very well for their World Cup hopes.

"It turned out to be a good game for our World Cup squad selection," he said.

"We can go home with a good result in a good atmosphere.

"Although we hadn't had much time to prepare, it was a good occasion for us to show the quality of our league by playing against a good side."