Deliver goods

Novak Djokovic of Serbia celebrates winning his men's singles tennis match against Juan Martin del Potro of Argentina at the ATP World Tour Finals at the O2 Arena in London, Nov 7, 2013. [Photo/Agencies]

"But, you know, I try to find that as an opportunity for me to get extra motivated to kind of push myself to the limit and deliver the goods when needed."

Del Potro, still only 25, has also been on a hot streak since the US Open, winning titles in Tokyo and in Basel where he beat Federer in his own backyard, and after beating Gasquet on Monday, looked in the mood from the start against Djokovic.

However, he paid for failing to convert break points in the opening game and Djokovic struck first blood in the sixth game with a succession of laser-guided groundstrokes that eventually proved beyond even the condor-like reach of Del Potro.

One break was sufficient to wrap up the first set but Del Potro was not finished and hammered away in the second, earning a decisive break in the sixth game with a netcord.

Del Potro piled on the pressure at the start of the third as he cranked up the power on his forehand wing.

Two break points arrived at 1-1 but once Djokovic had wriggled out of danger he did not look back.

Having beaten Federer and Del Potro so far here, the Serb was asked who he thought would win their showdown.

It was about his only moment of doubt all night.

"Roger is definitely playing better than he was throughout the whole year," he said. "He loves these conditions.

"But on the other hand, Del Potro has big serve. I can expect a three-set battle. I can't pick the winner."

Juan Martin del Potro of Argentina reacts during his men's singles tennis match against Novak Djokovic of Serbia at the ATP World Tour Finals at the O2 Arena in London, Nov 7, 2013. [Photo/Agencies]