The world number two was reacting to the verdict of the Court of Arbitration for Sport, which on Tuesday 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.
The player has always maintained the doping control officer (DCO) had assured him he would not face punishment.
The CAS panel accepted the DCO should have made sure he understood the gravity of the situation but found he had committed a doping offence.
The verdict came only 11 days after Croatia's Marin Cilic had his ban for failing a doping test reduced from nine months to four months by CAS.
Djokovic has been one of Troicki's most vocal supporters and, following his victory over Roger Federer at the Barclays ATP World Tour Finals, he arrived at his press conference with written notes on the case.
An angry and emotional 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.
"First of all, he's not positive on any banned substance. I'm not saying that it's completely not his fault.
"She (the DCO) did not clearly present him all the severe consequences that he will have if he avoids that. She told him that he needs to write a report and that he will be just fine.
"And because of her negligence and because of her unprofessionalism, he is now off the tour for one year. And now it makes me nervous as a player to do any kind of test.
"I don't have trust in them anymore. I don't have trust in what's going on.
"I don't know if tomorrow the (anti-doping) representative, because of their unprofessionalism, because of their negligence, because of their inability to explain the rules in a proper way, I don't know if they're going to misplace the test that I have or anything worse than that.
"For me, the whole procedure of the court case is totally against the player and player's rights.
"Now in Viktor's case, he's going to be sanctioned until July next year, and this lady, the DCO, she's going to come back tomorrow for the job. Nobody is going to answer for that. Only him. Why?
"For me, this is total injustice. It's just incredible."
The ATP, the governing body for players and tournaments on the men's tour, did not escape Djokovic's wrath.
He said: "After this kind of announcement and after this particular situation, the only one who is suffering here is the player. The ATP, which is supposed to be an association of players of tennis professionals, which is supposed to be the governing body, the association that stands behind the players, is not going to answer on this announcement, is not going to do anything for Viktor.
"So Viktor is there by himself. Tomorrow it can be anybody else. Cilic was there in this situation.
"I'm emotionally connected to Viktor but, looking at the whole scenario, it doesn't give me any trust in that, in them, in the whole procedure, in the whole rules, in anything.
"That's it. That's my statement. Sorry, but that's what I had to do. Not just because of him, but because of the sake of the players and because of the sake of the sport. It's just ridiculous."