The World No 2 was reacting to the verdict of the CAS, which ruled Djokovic’s fellow Serbian Viktor Troicki should serve a 12-month ban for missing a doping test.
Troicki had originally been suspended for 18 months by an International Tennis Federation anti-doping tribunal but had appealed to CAS to have the sanction overturned.
Troicki refused to take a blood test at the Monte Carlo Masters in April because he was feeling unwell and has a severe phobia of needles.
An angry Djokovic said: “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 does not work. I don’t have trust in them anymore. I don’t have trust in what’s going on.”