MELBOURNE - Defending champion Novak Djokovic returns to the Australian Open seeking his third consecutive trophy at Melbourne Park, where memories of last year’s gut-wrenching final against Rafa Nadal still linger around Rod Laver Arena’s blue centre court.Last year’s record-breaking epic of five punishing hours and 53 minutes secured Djokovic his fifth grand slam title while establishing the 25-year-old as tennis’s indisputable iron man.The marathon match would also serve as a portent for the year ahead for the steely-eyed Serb, who came under siege from his ‘Big Four’ rivals but emerged from an attritional season with his world number one ranking intact.If 2011 was the year Djokovic soared into the stratosphere on the back of three grand slam titles and an astonishing 41-match winning streak, he as brought gently back to Earth in 2012.After winning his third Australian Open, Djokovic would add no further major titles last year, with the spoils shared by Rafa Nadal, Roger Federer and Andy Murray.Federer, who shattered Djokovic’s Wimbledon defence in the semi-final on the way to his 17th major crown, would even prise the number one ranking away from the Serb before losing it again less than four months later.Djokovic would taste further disappointment with a semi-final loss to Briton Murray at the London Olympics, where he was also upset by Argentine Juan Martin Del Potro in the bronze medal match.Murray, a good friend off the court, would later quash Djokovic’s U.S. Open title defence in a gruelling five-set final.Rather than sulk in the shadows with the spotlight trained elsewhere, Djokovic responded by thrashing a succession of opponents to win his next tournament at the China Open.He then exacted partial revenge for his U.S. Open defeat by edging Murray for the Shanghai Masters title.INCREDIBLE 2011Federer’s failure to defend his Paris Masters title effectively handed the number one ranking back to Djokovic, but there was little debate over whether the Serb had earned it, as he stormed to victory in the season-ending ATP Tour Finals.The straight-sets win in the final over Federer gave him his sixth title for the season and was all the more impressive amid worries about his seriously ill father."I didn’t really know how I would follow up after my incredible 2011, but I believed that I have to use the time where I’m playing the best tennis of my life,” Djokovic said after winning his career-best 75th match of the year."It was a fantastic year, where I’ve had to face a lot of difficulties off the court as well.”