Haussler was born to a German father and Australian mother and raised in the town of Inverell, New South Wales, Australia, before leaving for Germany in 1998 at age 14 to pursue a dream of being a professional cyclist.

He looked set to be a rider of the future in the classics, in 2009 coming in second in both the Tour of Flanders and Milan–San Remo, narrowly beaten in the latter by Mark Cavendish in a photo-finish.

However, in a 2008 interview on CyclingNews.com, he suggested that he would no longer race for Germany as he wished to compete for Australia in the 2010 UCI Road World Championships in Melbourne.

"[7] The UCI, however, insisted that if Haussler wanted to ride for Australia he would have to give up his German citizenship, which the cyclist said in a November 2009 interview "is not open for debate at the moment".

[12][13] In the 2012 Tour of California, Haussler was denied victory on the four first stages of the race by Peter Sagan of the Liquigas–Cannondale squad, who beat him to the line each time.