Melbourne: The Novak Djokovic that bowed out of his first Australian Open title defence with heat sickness in 2009 has now been replaced by a mentally and physically tougher upgrade not prone to meltdowns, the world number two said.

After a rusty opening round, Djokovic`s bid for a fourth successive title at Melbourne Park shifted up a gear on Wednesday as he trounced Argentine Leonardo Mayer 6-0 6-4 6-4 in Rod Laver Arena to march to the third round on another day of stifling heat.

Players have grumbled about the conditions, and a Canadian in the men`s draw described the tournament`s organisers as "inhumane" after he fainted on Tuesday when temperatures peaked at 42 degrees Celsius (108 Fahrenheit).

In 2009, a 21-year-old Djokovic was criticised by players and pundits for pulling out of his quarter-final when trailing American Andy Roddick on a day of extreme heat, having earned a reputation for retiring when the going got tough.

There was little moaning from the Serb on Wednesday, however, after he wrapped up his match against 98th-ranked Mayer in less than two hours to escape the 40-degree heat.

Apart from the hat-trick of titles won at Melbourne Park from 2011-13, Djokovic said there were "plenty of differences" between himself and the 2009 model.

GAINED STRENGTH

"Obviously as the years go by, I`m more mature as a player, as a person. I learned new things in life. I developed myself," he said.

"I physically got stronger - mentally also. All of this plays, of course, an important role when you are playing in such conditions.

"It`s not easy. Maybe it looks (easy), but I do go through tough times after long rallies, as everybody, trying to get some air, obviously.

"Generally it`s much more efficient for me nowadays to recover and to get ready for the next point than it used to be in 2009 when I retired in my match against Roddick, yeah."

Djokovic completed his transformation into tennis`s undisputable iron-man by outlasting super-fit Spaniard Rafa Nadal to win the 2012 Australian Open in a final that lasted a grand slam record of just under six hours.


The 26-year-old plays Russian Dmitry Tursunov in the third round on Friday, another day forecast to exceed 40 Celsius.

"Everything is fine," Djokovic repeated like a Buddhist invocation during his post-match media conference when asked about his ankle which rolled during a first-set tumble against Mayer.

"I`m physically fit. I`ve been practising, preparing for the Australian summer that we all know can be difficult at times with the conditions.

"Knowing that I played a day match today, I prepared myself mentally for that.

"It`s not just physically. Mentally you need to be tough enough to not give up and not think about what conditions can do to you."