Often known as 'the Djoker' for his famous tennis player impersonations, Novak Djokovic is certainly not joking around with his current form on court.

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The 2008 Australian Open champion has converted himself into the prime candidate to attain the London ATP World Tour finals starting in five days' time.

Djokovic has won three of the past four events he has participated in, including the China Open and the Basel tournament, in which he defeated world No.1 Roger Federer in the final.

The Serbian's most recent victory against Frenchman Gael Monfils in the final of the BNP Paribas Masters in Paris, showcased all the traits necessary to see the 22-year-old provide stiff defence to his 2008 ATP Tour finals crown.

Playing against a vocal French crowd, Djokovic was pushed to the limit by one of the more talented, yet enigmatic opponents on the ATP tour.

After winning the first set fairly comfortably, he found himself fighting desperately for every point as Monfils brought the crowd to life with his array of sensational shot making.

Despite making do with a lot of momentum, Monfils eventually succumbed to Djokovic's experience in the latter stages of big tournaments, falling short in the tie-breaker to hand the Serb his fifth ATP title this year.

The victory has laid the platform for Djokovic to dominate the upcoming Tour finals in London, considering he is the only player currently performing at full fitness.

Main rivals Federer, Rafael Nadal, Andy Murray and Juan Martin del Potro have suffered injury-interrupted preparations following the US Open, and hardly have the recent form on the board to trouble the reigning champion.

Federer, in particular, took an extended break after losing the US Open final, choosing to withdraw from the Japan Open and Shanghai Masters due to injury and family reasons.

His time back on court has produced lean results for a player of his standing, losing in the final of the Davidoff Swiss indoors to Djokovic in his first tournament back from injury.

The Swiss maestro followed this result with a lean showing at the Paribas Masters, losing to unseeded Frenchman Julien Benneteau in the second round.

The loss continued Federer's lack of success in Paris, where he has not made it past the quarter-finals in his last six attempts.

World No.2 Nadal is another who has struggled severely to replicate his best form against the likes of Djokovic and Co.

The Spaniard, who is slowly regaining full fitness, was blown away by the Serb at the Paribas Masters, losing in straight sets.

Before that, Nadal also suffered unexpected defeats to Marian Cilic at the China Open and Russian Nikolay Davydenko in the Shanghai Masters final.

Current US Open champion Del Potro has also found it difficult to produce his best form of late, exiting early at both the Japan Open and the Shanghai Masters, before retiring in Paris against Czech player Radek Stepanek in the quarter-finals.

Probably the only player that has showcased enough glimpses of form to trouble Djokovic in London is Murray.

Whilst nowhere near his best form, the Scot has had more success than Federer, Nadal and Del Potro of late, winning the Valencia Open.

The World No.4, however, suffered a below-par loss to Radek Stepanek at the Paribas Masters, citing exhaustion as the reason for defeat.

With arguably four of the world’s top five players seemingly running out of puff towards the end of the season, Djokovic is finishing 2009 with a head of steam - and currently looks a sure bet to emerge victorious in the last big tournament the ATP season has to offer.

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