Young Australian professional cyclist David McPartland will start stage three as the unlikely leader of the Tour Down Under.

McPartland combined with Dutchman Alain Van Katwijk and fellow Australian Patrick Jonker in a brave attack which decided Wednesday's second stage.

The 23-year-old, who signed a professional contract only a fortnight ago with Italian division two team Tenax, outsprinted Van Katwijk at the end Wednesday, with Jonker third.

The trio is nearly three minutes ahead of the next riders on general classification, with top Australians Baden Cooke and Robbie McEwen among a large group at 1min 51sec.

Stage three will be a tough 150km stage from Goolwa to Victor Harbour, south of the city.

Defending champion Mikel Astarloza of Spain is already out of the running after losing nearly half an hour in the 157km stage from Norwood to Kapunda.

McPartland, Van Katwijk and Jonker broke away in the first few kilometres to set up their trifecta.

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