Roger Federer said he trusts the anti-doping procedures in tennis despite rival Novak Djokovic's claim that fellow Serb's Victor Troicki's one-year ban was the result of negligence by the authorities.
The 17-times grand slam champion still thinks that players are not tested regularly enough, however, even if the International Tennis Federation (ITF) has taken steps to bolster its stance against doping.
Troicki learned this week that his appeal to the Court of Arbitration for Sport (CAS) against an 18-month ITF ban for refusing to give a blood sample at the Monte Carlo Masters in April had been only partially successful with his sanction reduced to 12 months.
That prompted a furious response from Djokovic at the ATP World Tour Finals this week with the world number two declaring he no longer trusted the sport's anti-doping controls.
Federer offered a more measured view on Thursday after beating Richard Gasquet 6-4 6-3 to stay on course for the semi-finals at the season-ending tournament.
"Overall I trust the system," the 32-year-old told a news conference. "I think they're all very professional.
"I just think it's very important that they treat us like normal human beings, not criminals. It's fine to treat a guy bad if the guy tested positive, the guy needs to feel the pain, but not if you haven't done anything yet."
Troicki blamed his ban on a Doping Control Officer (DCO) at Monte Carlo, insisting that the official told him he could delay giving a blood sample until the following day because he had felt unwell and had a phobia for needles.
He subsequently provided a blood sample that was negative, as was his urine sample, but was punished after the ITF's independent tribunal in July found he had broken the rules.
A CAS panel confirmed Troicki had committed an Anti-Doping Rule Violation under Article 2.3 of the Tennis Anti-Doping Programme, but said his "fault was not significant" and that the rules had not been communicated to Troicki clearly enough.
Federer, however, said rules were rules.
"I don't know the conversation, the situation, exactly what happened," he said. "I guess, the chaperone, the guy who comes and is next to you like a shadow (during the doping test), sometimes you don't know who that guy is.
"Sometimes they're a little hesitant because you just lost a match and you look extremely angry, so they don't dare to talk to you. They should probably just introduce themselves.
"It just becomes really complicated. But I do believe that when you are requested for a sample, you have to give the sample. It doesn't matter how bad you feel. I'm sorry."
The ITF earlier this year said it was introducing the biological passport system, following calls for more anti-doping measures.
However, Federer believes there is still not enough testing, with only 187 blood tests carried out in 2012.
"I didn't get tested in Basel, I don't think. I didn't get tested in Paris, I don't think. I got tested here after the first match," Federer said.
"I just feel like there needs to be more testing done. I think I was tested 25 times in 2003, 2004. Ever since, I think it's been clearly going down this season.
"You just show up and test a guy that's winning everything. That's sometimes what I struggle with."