Grand Slam champions Roger Federer and Novak Djokovic became the latest targets of criticism by the International Tennis Federation following their "unfair" comments to the current anti-doping system.

Federer and Djokovic, two of the finest tennis players in the world, voiced out their opinions about the anti-doping system, and the way it is conducted.

Federer, who has been vocal in his stance against doping in the sport, believed the anti-doping system is uncontrolled. Meanwhile, Djokovic said he doesn't trust the World Anti-Doping Agency anymore following the 12-month suspension imposed on fellow player and friend Viktor Troicki for refusing to take a drug test.

"I think it's not just 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 what's going on," Djokovic told Tennis Tonic.

"The ATP, who is supposed to be an association of tennis professionals, who is supposed to be the governing body, the association that stands behind the players, are not going to answer on this announcement, are not going to do anything for Viktor. So Viktor is there by himself," said the former top-ranked netter.

Unfair Criticisms?

ITF Anti-doping manager Stuart Miller fired back at Federer and Djokovic, calling their criticism about the anti-doping system unfair. Moreover, Miller stressed the system is working pretty well, according to its purpose.

"I think that tennis is doing a good job in the programmes it has and we've had two fairly high-profile cases recently with Marin Cilic and Viktor Troicki and let's not forget both of those cases resulted in violations for the athletes concerned," Miller said via Tennis Tonic.

"To me that shows that the programme is successful in catching the people it is supposed to be catching so I don't think it's necessarily fair criticism. Our programme includes in-competition and out-of-competition testing, with both urine and bloods samples taken and the recent introduction of the athlete's biological passport, another too," he added.