World number two Novak Djokovic has slammed the anti-doping programme in tennis following Viktor Troicki's failure to have his doping ban completely overturned.
The Court of Arbitration for Sport reduced the Serbian's ban from 18 months to one year after he was suspended by the International Tennis Federation in July.
Troicki failed to provide a blood sample at the Monte Carlo Masters earlier this year, claiming that he was too unwell to carry out the task at the time.
"First of all, Viktor is a very good friend of mine," Djokovic said in a press conference. "It's very bad news that we got for him, and for me, for all of us who are close to him.
"But I think it's just not bad news for him, it proves again that this system of WADA and anti-doping agency does not work. I don't have trust in them anymore. I don't have trust in what's going on."
Djokovic was speaking after beating Roger Federer in three sets in the round robin stage of the ATP World Tour Finals in London.
