Anthony Joshua believes he would never be allowed to box again if he had Alexander Povetkin's history of doping cases.
The 38-year-old Povetkin twice tested positive for performance-enhancing drugs during an eight-month period in 2016, but he has continued to fight and earned the status of mandatory challenger to Joshua, the WBA, WBO and IBF heavyweight champion.
Both fighters have signed up to the Voluntary Anti-Doping Association's (VADA) programme ahead of their September 22 date at Wembley Stadium and have already been tested twice, but questions persist over whether Povetkin should be given such an opportunity.
He tested positive for meldonium and later ostarine, preventing fights against WBC champion Deontay Wilder and then Bermane Stiverne, but served a suspension only with the WBC so consistently remained in a position to fight.
The Russian maintains he is innocent, but the 28-year-old Joshua - perhaps the world's highest-profile fighter - said: "I would never be able to box again because I would be made an example of. If I missed a drugs test or am an hour late then people will say 'Oh, he must have been doping'.
"I am not the lawmaker on that stuff. I would rather take a loss than be done for doping; being done for doping is far worse for your legacy than taking a loss.
"I don't see doping as a way of making yourself better - if a person is better than you then work harder, train harder, you don't need to dope.
"Weigh it up; doping, being banned, legacy damaged. Or someone is better than you on the night, give them the respect and bounce back.
"I would rather stay clean and give it my best every time.
"When he is fighting me it will be a straight and clean fight. His past is his past and they dealt with it however they did. If I got done for doping - it would never happen - then they would deal with me."
Povetkin fought for the same titles when suffering his only defeat against Wladimir Klitschko on the same night in 2013 that Joshua made his professional debut and stopped Emanuele Leo.
Povetkin is also friends with Russian president Vladimir Putin, and Povetkin said: "I am very well deserved of the fight I am getting. I am here for a reason, this was a mandatory. I got to this point. I had to defeat other opponents in order to get this position.
"I was caught on meldonium, and it was a nanogram quantity. And it happened right before the fight. I was clean a couple of tests before it, and I was cleaned when tested after that. For me it was very, very suspicious. I know that I am clean. I know that I was clean back then.
"I was accused of wrongdoing when I wasn't. The second time, ostarine. I don't know what it is. They said it is for gaining muscle; I only weighed 100kg for that fight. A couple of tests before I was caught were clean.
"And the time they found it, the time before the fight, was very, very minor in quantity. Doesn't it all sound a little suspicious? In my opinion there was something going on at that time.
"What did I do? Right before the fight I licked some meldonium or some ostarine to have no affect? Does it sound realistic to you?
"I don't think that our sportsmen in Russia consume all those things (drugs) they are accused of. As an amateur I understood myself what we consumed and what we were taking, and I can assure you there was nothing prohibited."