Matthews furious, Rohan Dennis leads Tour

Michael Matthews has blasted the lack of respect in the peloton and angrily confronted a rival after his Tour Down Under overall hopes were dramatically dashed.

Matthews' wife Kat stepped between him and American rider Magnus Sheffield after the stage as words were exchanged.

The Australian cycling star's disastrous mechanical problem at a crucial point in Thursday's second stage opened the door for compatriot Rohan Dennis to take the overall lead.

Had Matthews not dropped his chain early on the last climb, about 20km from the stage finish, he most likely would have the overall lead going into Friday's pivotal Corkscrew stage.

Instead, he lost two minutes 13 seconds as Dennis and a select group of four other riders decided the 154.8km stage from suburban Brighton to Victor Harbor, south of Adelaide.

It was a dramatic end to the stage - not long after Matthews' overall hopes were dashed, Italian race leader Alberto Bettiol (EF Education) dramatically lost contact with the peloton and crawled to the finish, suffering leg cramps.

Immediately after Matthews finished, he angrily confronted young American Sheffield (Ineos Grenadiers).

Matthews' wife Kat then moved to ensure the incident did not escalate.

"I don't even know what's happening in cycling these days," Matthews told the Seven Network immediately before having words with Sheffield.

"There's just no respect in the bunch.

"I was in a great position and then I was hit from one side, hit from the other side.

"I dropped my chain, it got stuck between the frame and the front crank, I couldn't get it out and I couldn't get my time back."

There are growing concerns in the peloton about a lack of etiquette among riders and that lack of respect was blamed for a spate of crashes during stage one.

Sheffield later defended himself, saying another rider had bumped into him and he then made contact with Matthews.

"There was a bit of touching of wheels. I immediately apologised after the finish line, it's really unfortunate - this is part of cycling and racing," Sheffield said.

"It wasn't my intention at all and I really just tried to apologise and be up front with him."

Matthews' mechanical issue came at just over 20km left, as the peloton tackled the last climb of the stage at Nettle Hill Road.

He had picked up three more seconds in intermediate sprints, meaning he only trailed Bettiol by three seconds.

Matthews also dropped his chain late in stage one, but rallied to finish third.

Immediately after Matthews' disaster on Thursday, Dennis and his breakaway companions went clear.

As Matthews dealt with his disaster, Jayco-AlUla teammate Simon Yates cleverly joined the talent-packed break.

Reigning Giro d'Italia champion Jai Hindley (Bora-Hansgrohe), newly crowned Australian time trial champion Jay Vine (UAE Team Emirates), Dennis (Jumbo Visma) and Swiss Mauro Schmid (Soudal Quick-Step) also went on the attack.

The breakaway stayed clear and Dennis launched a solo charge late to take the stage.

He leads Vine, who was second on the stage, by three seconds overall.

It is a welcome morale boost for Dennis' Jumbo-Visma team after their Dutch star Robert Gesink crashed out of the race on Tuesday with a fractured pelvis.