Novak Djokovic is hoping he will deal better with the pressure of defending a big title than he did the first time around when he takes to the court at London's O2 Arena in the Barclays ATP World Tour Finals this week.

The Serbian had the tennis world at his feet when he won the Australian Open last January at the age of 20 but, instead of lifting a weight off his shoulders, Djokovic spent 18 months struggling to live up to his own and others' expectations.

Indeed, his victory at last year's end-of-season showpiece came as something of a surprise and it is only in the last couple of months Djokovic has rediscovered the form that made him the Tour's most exciting young player.

The defence of his title in Melbourne ended in retirement against a rejuvenated Andy Roddick in the quarter-finals but he feels he is now better placed to deal with the situation.

The 22-year-old said: "This year I have tasted, in Australia, for the first time the role of defending a major title and it wasn't really a fun time. I was mentally very frustrated at times and unfortunately I finished in the quarter-finals the way I finished.

"But, on the bright side, I've learned a lot of things and I've tried to take the best out of it. I rate the World Tour Finals alongside grand slams as the biggest event in our sport so being a title defender is obviously a big responsibility.

"At the start of the year, even though I had the best clay-court season in my whole career up to Roland Garros, I was going through tough times because I made some major changes with my racquet.

"It's a big change to make and I took the responsibility. It kind of affected me on the court and I was maybe paying too much attention to some things off the court, I maybe kept my focus out of tennis too much.

"But I stabilised the last two months and matured more, and I know what I want to do on the court. I'm happy."

By beating Roger Federer in the final of the world number one's hometown tournament in Basle then lifting the trophy at the Paris Masters, Djokovic has established himself as arguably the man to beat in London this week.

The Serb opens his campaign in the round-robin event against Nikolay Davydenko on Monday, while Rafael Nadal faces Robin Soderling in the other Group B match.

The draw means Djokovic will renew his rivalry with world number two Nadal, who he demolished in the semi-finals in Paris.

And the Spaniard does not hold out much hope of reversing the result, saying: "He played very well. If I played my best tennis and he played like he did, it's going to be almost impossible to beat him. He's definitely the player who arrives playing best."

Djokovic's run of success means he also arrives in London as the player who has spent the most time on court recently and, at the end of a long season in which he has played almost 100 matches, that may yet take its toll.

The world number three, though, is optimistic he can hold it together for one more week.

"I think it's a very mental game and generally a lot of things come from your head and, even though you're running out of physical energy, you can still motivate your body to do well on the court," he added.