Novak Djokovic lauds his friend Viktor Troicki for doing exceptionally well in his return to the tour following a doping suspension. His fellow Serb, who was unranked a week into his comeback, defeated Mikhail Youhzny and David Ferrer in consecutive events, and looks like he will be back inside the Top 150 in just three months.

"He started from scratch, zero points. He had to play I think couple times qualifications of Challengers," said Djokovic. "To go down and play, you know, qualifications of a Challenger, it's definitely different. He handled it very well. I have to say we all expected him to do well. But this fast to get to 150 of the world, already play here second round and win against players like Ferrer last week and this week Youzhny, it's pretty impressive."

Troicki received a suspension last year for refusing to take a blood test, which was reduced in length after an appeal. Troicki said he was not properly instructed by an official conducting the test.

While not playing, Trocki was invited to train with Djokovic, who believes his friend was penalized unfairly. The world No. 1 said he had a natural desire to help him return.

"I know him since we were eight and nine years old. That's the first time we played against each other actually in a tournament in Belgrade," said Djokovic.

"Ever since then we are very good friends. He's definitely one of the closest friends I got on the tennis,” he said. “He’s my best friend next to Janko [Tipsarevic] and [Nenad] Zimonjic. We won Davis Cup together. But most of all we have this personal relationship."

Djokovic added that he expects Troicki to return to the Top 100 by the end of this season.