World number one Novak Djokovic did not let friendship prevent him from carrying on where he left off last month when he made a successful defence of his Australian Open title at the Dubai Open on Tuesday.

Djokovic’s attempt to win back the Dubai Open title began with a 6-1 6-4 win over Viktor Troicki, the fellow Davis Cup player with whom he grew up and shared tennis courts many times in the city of Belgrade.

The top-seeded Serbian moved so swiftly and turned defence into attack so suddenly that it was hard to believe four weeks had passed since he last played singles on the ATP tour.

Earlier, Australian Bernard Tomic retired with a “general illness” trailing Romania’s Victor Hanescu 3-2.

And Argentinian Juan Martin Del Potro nearly did not survive beyond the first round.

Del Potro had to save four match points to beat Marcos Baghdatis, the former Australian Open finalist from Cyprus, by 4-6 6-4 7-6 (7-4).

Nikolay Davydenko, who hopes to return to the top 20 this year as part of his farewell to the tour, brought comedy as well as an upset as he reached the second round.

The former world number three from Russia beat Janko Tipsarevic, the sixth-seeded Serbian, 6-0 7-5, but took half an hour to capture the first two games, and 50 minutes to win the love set.

“After two games I was thinking ‘match just starting – and I’m already tired’, he said, creating a haggard expression.

Davydenko had a comic explanation for the sharp twist in the second set of a match which, having dominated, he found himself trailing by two breaks of serve.

“Really before the second set he, like, go to toilet and come back and start to play better. I don’t know what he did there,” he said.