A sprint finish was expected at the conclusion of the 129 kilometre flat stage from North Adelaide to Port Adelaide.

Lead out trains proved unorganised in the closing stages, with sprinters having to battle to hit the front of the race as the finish drew closer.

Germany's Max Walscheid appeared best placed to claim the opening stage win of the race, with the Team Sunweb rider reaching the front in the closing metres.

He was denied success by the fast finishing Viviani as the Italian national champion swept past to secure the win.

The Deceuninck-QuickStep sprinter crossed the line in a winning time of 3 hours 19min 47sec.

Walscheid and Italy's Jakub Mareczko would complete the top three on the same time as the stage winner.

There was disappointment for two of the favourites for the stage, with Slovakia's Peter Sagan finishing eighth after being caught up in a chaotic finish.

Australia's Caleb Ewan, who beat Sagan in the one-day People's Choice Classic on Sunday (January 13), finished further down in 22nd.

Viviani heads the general classification with bonus seconds earned for the stage win giving him a four second advantage over Walscheid.

Racing will continue tomorrow with a 122 kilometre stage from Norwood to Angaston.

Organisers reduced the stage by nearly 30 kilometres over fears of potentially high temperatures.

The six-day race will take place until Sunday (January 20) when a climbing stage from McLaren Vale to Willunga Hill could prove decisive in deciding the winner.