Australian William Clarke won the second stage of cycling's Tour Down Under on Wednesday, defying the peloton in one of the boldest individual breakaways in the history of the WorldTour event.

26-year-old Clarke was the last rider selected for the six-stage tour when he was added to the UniSA team after finishing fifth and winning the sprint classification at the Australian national road championships.

He made the best of a rare appearance in elite professional company Wednesday, first joining Switzerland's Martin Kohler in a two-man break, then leading on his own for half of the 92-mile stage from Lobethal to Stirling in the Adelaide Hills.

Clarke led an Australian sweep at the podium as Michael Matthews finished second and Simon Gerrans third.

Clarke and Team BMC Racing's Swiss time trial champion Martin Kohler broke away from the peloton after less than a mile of Wednesday's stage and were more than 10 minutes (or 2 miles) ahead after 25 miles.

Kohler started the day in third place on general classification and only 4 seconds behind first-stage winner and race leader Andre Greipel of Germany.

He picked up a 3-second time bonus when he won the first intermediate sprint, to close within a second of Greipel, then took the overall lead on the road when he also won the second intermediate sprint at the 39-mile mark.

Kohler then sat up and fell back to the peloton while Clarke continued on his own.

"It's really unbelievable," Kohler told Roadcycling.com and Roadcycling.mobi after being celebrated on the podium and continued "I had a good day and a good place with the best riders in the end and that brought me into the lead overall. To be in a WorldTour leader's jersey is very good so far. I am very happy."

Clarke's lead peaked at more than 12 minutes and he was still 10 minutes, 50 seconds ahead at the 61-mile mark.

When the peloton roused itself, it closed quickly but Clarke was able to stay ahead over three 20-kilometer laps through the finish line at Stirling.

After 132 kilometers, his lead was down to 5 minutes, 5 seconds; with 10 kilometers to go he led by 4 minutes, 20 seconds and 5 kilometers from the finish he was still in front by 4 minutes, 10 seconds.

He was still able to hold the peloton at bay by more than a minute to achieve his most important professional victory.

"This is unbelievable really," Clarke said. "I was up the road with a BMC rider (Kohler) to get some sprint points and I kept going when he went back to the peloton.

"I was dying in the last 10 kilometers," Clarke continued and added "(Team Manager) Dave Sanders was telling me to go for the general classification. It's amazing that a breakaway rider can stay away for so long. It's sort of my speciality to keep going."

Riding in a team car, Team BMC Racing owner Andy Rihs said he admired the team's strategy and work to put Kohler in the leader's jersey. "I think it's unbelievable because I didn't expect a move like this," Rihs said and added "I'd have to say the [team's] strategy to go for the chase for the bonus seconds really worked out well in the end. It was perfect actually. We are all very excited about that. It's great for Martin (Kohler), the BMC Racing Team and the team of Cadel Evans here in Australia."

Unfortunately two riders were unable to start Wednesday's stage after suffering serious injuries in a crash 800 meters from the start of the first stage, reducing the peloton to 131 riders.

Jurgen Roelandts of Greipel's Lotto-Belisol team was at Royal Adelaide Hospital with a fracture to the C6 vertebrae in his neck. The fracture was stable and he does not need surgery.

Frederic Guesdon, of the FDJ-BigMat team, suffered a broken pelvis.