Novak Djokovic on Friday slammed the World Anti-Doping Agency (WADA) once again over a ban imposed on his compatriot Viktor Troicki, after he was accused of being "misinformed" by the global body.
"For me this is total injustice and it shows again that the system does not work and there is nothing that they can say to convince me," the Serbian tennis world number two told reporters.
Minutes earlier, he handed Serbia a 1-0 lead over defending champions the Czech Republic in the Davis Cup final in Belgrade by beating Radek Stepanek in straight sets.
The Serbian team has been remarkably weakened by the absence of injured world number 36 Janko Tipsarevic -- and of the 76th-ranked Troicki.
Troicki was handed an 18-month ban for refusing to take a blood test at the Monte Carlo Masters in April because he was feeling unwell and has a severe phobia of needles.
Troicki insists the doping control officer (DCO) had assured him he would not face punishment.
On November 5 the Court of Arbitration for Sport rejected Troicki's plea to lift the ban, only reducing the sanction to 12 months.
The day after, at the ATP Tour Finals in London which he won on Monday, Djokovic offered an angry diatribe against the WADA fuming at the "negligence and unprofessionalism" of the DCO.
Outgoing WADA president John Fahey struck back on Friday when he told CNN that Djokovic's statements were not "informed."
"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 said.
But Djokovic remained adamant.
"I'm not going to call him because I know more than he thinks that I know," he said.
Fahey will step down as WADA chief in January to be succeeded by International Olympic Committee (IOC) deputy president Craig Reedie who was elected head of the world body in Johannesburg on Friday.