Germany's Phil Bauhaus (Bahrain Victorious) held off fast-finishing Australian Caleb Ewan to narrowly take out the first stage of the men's Tour Down Under in Adelaide on Wednesday.

Bauhaus had less than half a wheel to spare as he flashed across the finish line in Tanunda as Ewan (Australian National Team) stormed home from well back in the pack at the end of the 149.9km stage through South Australia's Barossa Valley wine growing region.

Australia's Michael Matthews (Jayco-AlUla) was third across the line from Italy's Alessandro Covi (UAE Team Emirates).

Italy's Alberto Bettiol (EF Education First) led the TDU overall after his win in Tuesday's Prologue around Adelaide's streets.

Bauhaus recovered from a crash earlier in the opening stage to get in position for a crack at the finishing sprint down the main street of Tanunda.

"I crashed pretty bad, it was a massive impact, but I recovered and the team did a really good job, we were always in front in the last lap," Bauhaus said.

"In the (lead up) Schwalbe Classic I waited too long, so this time with 300 metres left I just went for it and it was pretty close at the end with Caleb, but I'm super happy.

"I did not want to celebrate early. I was only sure I won later. It was super nervous today. A lot of guys went down."

The stage was marred by a series of pile-ups and a few riders came down in a scrimmage in the closing furious kilometre.

American Magnus Sheffield (Ineos Grenadiers) went down in the final run and sustained cuts on both knees. He was able to cross the line, retaining his third place overall. His team said he was being evaluated.

Ewan relished the rough and tumble in the closing stages, tweeting: "Doesn't get better than a big crash does it?"

There was also a mass fall with 50km left with a half dozen riders tumbling onto the bitumen. Dutchman Robert Gesink (Jumbo-Visma) and New Zealand's Patrick Bevin (DSM) could not continue in the stage.

Matthews, making his first appearance in the TDU since 2014, pulled a few seconds back on race leader Bettiol through time bonuses and was satisfied with his day's work.

"I wouldn't have minded a bit harder stage today. We nailed the two intermediate sprints," Matthews said.

"It was a successful day to try to set me up for the overall.

"When you're that close to a win you're going to be disappointed. Overall it was a good day for us."

Matthews lies second overall, six seconds back, with Sheffield slipping to third at eight seconds behind Bettiol heading into Thursday's Brighton to Victor Harbor second stage raced over 154.8km.