- WADA president John Fahey replies to Novak Djokovic's criticism
- World No. 2 tennis star said he'd lost faith in agency after Viktor Troicki's ban
- Fahey tells CNN that Djokovic "hasn't got the faintest idea what we do"
- He says Lance Armstrong case shows that no-one is above the regulations
World Anti-Doping Agency (WADA) president John Fahey has told CNN he doesn't think Novak Djokovic "has the faintest idea" what his organization does after the former world No. 1 said he'd lost faith in the system.
The Serbian labeled compatriot Viktor Troicki's 12-month ban from tennis for missing a drugs test a "total injustice" and said he was now nervous to give any sort of sample.
But Fahey dismissed the six-time grand slam winner's comments as unhelpful and said it was up to the sport to do more to fight against doping.
"I don't think Novak Djokovic has the faintest idea what we do and if he wants to understand what we do I'm more than happy to pick up the phone and talk to him, if he wants to talk to me," he told CNN.
"If he wishes to then make a comment I might listen to him but for the moment I don't think that was an informed statement."
WADA's role in the fight against doping in sport has been in the spotlight in recent months after a string of athletes failed tests in Kenya and Jamaica.
And as well as Troicki, Croatian tennis star Marin Cilic also served a ban for doping offenses after taking a prohibited substance contained in supplements bought from a chemist.
Those cases have provoked disagreement within the game as to the best course of action, with Wimbledon champion Andy Murray calling the pair's actions "unprofessional."
Roger Federer, winner of 17 grand slams, said more testing needed to be done within the sport and also said players should give a sample when requested.
But when asked if he knew how widespread doping in tennis was, Fahey replied: "No I don't and nor do I think tennis knows how widespread it is.
"What I do know is they have a program and a commitment has been given. Can they do more? Every sport can do more.
"And when you get criticism from some of the champion tennis players about the number of times they've been tested then I hope tennis takes notice of it. I know they have and I believe that they'll address it."
Fahey also said the fall from grace of cyclist Lance Armstrong had been the best anti-doping message since he became WADA president in 2007.
In January, Armstrong -- following years of strenuous denials -- admitted to doping throughout his storied career, after he had been stripped of his seven Tour de France titles.
But Fahey thinks Armstrong's descent has proved that drug cheats will be caught out and punished no matter what their status.
"I think the Lance Armstrong story was the best message in my six years as to the effectiveness of the anti-doping programs," he explained.
"What that said to me and the rest of the world was no matter how big you are, how tall, how successful you are, you can get caught and be dealt with. That man has been destroyed in terms of reputation and in terms of, perhaps, many other aspects of his life.
"He's been seen as a cheat, a bully, a liar -- there's no doubt about that. Once upon a time he was revered as one of the greatest champions in his sport, of all time.
"The fact that someone as big as that is ultimately brought to justice shows that our code is effective."
As for athletics, Fahey acknowledged that doping is "widespread" and said part of the reason might be that there are different resources available to tackle the problem in different countries.
Kenya has had 17 athletes banned for doping offenses since 2012, while former 100 meters world record-holder Asafa Powell and three-time Olympic gold medalist Veronica Campbell-Brown are among six Jamaicans to have tested positive this year.
Fahey said doping is not just a problem in successful sporting countries like Kenya and Jamaica, but rejected the notion performance-enhancing drugs were beginning to ruin sport.
There had been a suggestion that certain countries could be banned from the Olympics if they refused to comply with anti-doping programs -- raising the prospect of Jamaica's six-time Olympic champion Usain Bolt missing out -- but Fahey said that was for the International Olympic Committee to determine.
"Should the Iinternational Olympic Committee take stronger steps? I'm sure if the evidence is there on the basis of difficulties with compliance in any particular country they would look seriously at that," he said.
"I think we have to stop for a moment and say, 'What is actually going on in Jamaica?' They do have an anti-doping program, it has not been effective, it has not been as good as it could have been and that's what WADA examined.
"We now have given them recommendations and we've got a commitment to say, 'Yes we dropped the ball but we've picked it up again and we'll get it right and we'll do that quickly.' "
Fahey also said that WADA's revised code, which is due out this week, would allow the agency greater investigative powers and called it a "great jump forward."