However, Bennett's goals are later in the season – targeting May's Giro d'Italia and July's Olympics road race - and he acknowledged he wasn't in top condition compared to some of his fellow contenders for the first race of his season, meaning there will be few concerns about being slightly off the pace.
His team were perhaps expecting more though, having hit the front on the base of Willunga Hill to set a high tempo. Antwan Tolhoek's rapid efforts tore the peloton to pieces, with only a select few riders able to follow his pace, but Bennett wasn't one of them, sliding back down the group.
Porte, who had won on Willunga Hill for six straight years, looked set to do it again as he dropped all his rivals and started to pick off the remnants of the breakaway. He caught the breakaway leaders with 700 metres to go, but needing to ride a steady tempo to win the race overall, it allowed unheralded Brit Matthew Holmes to hang on his wheel, before Holmes sprinted past in the final metres to claim a shock victory.
Porte had done enough to win the tour overall however, claiming victory by 25 seconds, while Bennett finished 46 seconds off the pace.
Bennett will now weigh up a potential trip to New Zealand nationals against heading over to Europe early, with his next race on the World Tour set to come in March at Paris-Nice, where he finished sixth last year.