Australian cycling star Jay Vine has fired the first shot in the battle for overall honours at the Tour Down Under.
The UAE Team Emirates rider finished fourth in the Tuesday prologue time trial to steal a small march on his general classification rivals at the Santos Tour.
The Australian time trial champion trails British prologue winner and overall leader Sam Watson (Ineos Grenadiers) by four seconds.
Vine is part of a potent three-rider overall threat for UAE Team Emirates at the Tour, alongside defending champion Jhonatan Narvaez from Ecuador and British star Adam Yates.
Narvaez is 23rd overall, nine seconds off the pace, while Yates is at 17 seconds.
In past Tours, that big a time gap would have written off Yates' chances. But this is the hardest route in race history.
After Watson's Australian teammate Sam Welsford and the other sprinters most likely battle for the stage win on Wednesday in the Barossa town of Tanunda, the contest for overall honours will start.
Stage two on Thursday will feature two climbs of Corkscrew Rd in the Adelaide Hills.
Like stage three of the women's Tour on Monday, this will be the first time in race history that the men have gone up the short but tough Corkscrew climb twice in a stage.
But after the second Corkscrew climb, the women had a high-speed descent to the finish and Swiss ace Noemi Ruegg was able to exploit that as she successfully defended her Tour title.
The men have no such climbing relief, finishing the stage in the Hills town of Uraidla, and a small break could dramatically affect the overall standings.
Before that first significant milestone, Wednesday will feature Watson, wearing the race leader's ochre jersey, helping the team lead out for Welsford at the stage finish.
The overall lead usually means that rider is protected by his team. But the stage win will be more important for Ineos Grenadiers, who recruited Welsford this season to replace compatriot Caleb Ewan as their sprinter.
