In the 2015 Australian Open, the defending champion had reached a career high ranking of what?
2015 Australian Open – Men's Singles: Stan Wawrinka was the defending champion, but he lost in the semifinals to Novak Djokovic. Stan Wawrinka:  Professionally called "Stan", he reached a career-high Association of Tennis Professionals (ATP) world No. 3 singles ranking for the first time on 27 January 2014.
world No. 3