LONDON - Anthony Joshua believes he would be forced to quit boxing if the unified heavyweight champion ever endured the kind of doping scandals that have engulfed Alexander Povetkin.

Povetkin's standing as the mandatory challenger for British star Joshua at Wembley on Sept 22 has infuriated fans, who feel the Russian shouldn't be allowed back on the big stage after his drug issues.

In May 2016, the 38-year-old tested positive for meldonium－the same banned substance compatriot Maria Sharapova was suspended from tennis for taking.

The failed test led to Povetkin's scheduled fight against Deontay Wilder being scrapped before the WBC accepted the explanation that he stopped taking the drug before it was on the banned list that year.

That wasn't the only black mark against Povetkin. In December 2016 he was found to have taken a banned muscle-building drug called ostarine.

He was suspended from WBC-sanctioned fights after the second failed test, but appealed and was allowed back into the sport with a yearlong ban and a $250,000 fine.

Both Joshua and Povetkin have signed up to the Voluntary Anti-Doping Association's (VADA) program ahead of their Wembley date and have been tested twice.

Reigning WBA, IBF and WBO champion Joshua－who has never been linked with doping－said a fighter of his profile would be made to pay a heavy price if he was found to be involved with substance abuse.

"I would never be able to box again because I would be made an example of. If I missed a drug test or I'm an hour late, people will say 'Oh, he must have been doping'," he said at Wembley on Wednesday.

"I am not the lawmaker on that stuff. I would rather lose 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 if 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.

"If I got done for doping－it would never happen－then they would deal with me."

Povetkin is adamant he did nothing wrong on either occasion and therefore shouldn't be regarded with suspicion when he faces Joshua.

"First of all, I have been cleared of that suspension. I have been justified. And the court case that was ongoing with the team of Wilder has finished in our favor," Povetkin said.

"For me it was very, very suspicious. I know that I am clean. I know that I was clean back then. All I can say is that I was accused of wrongdoing when I wasn't.

"After the first time I was caught I signed up on a secondary anti-doping testing program. Then what did I do? Right before the fight I licked some meldonium or some ostarine to have no effect and be caught with it right before the fight?

"Does it sound realistic to you? The amount they found doesn't give any effect, so why would I ever want to do that.

"I have nothing to do with it, and I am very well deserved of the fight I am getting."

Povetkin isn't the only Russian to have been tarnished by allegations of doping in recent years.

Forty seven Russian athletes and coaches were banned from this year's Winter Olympics after an investigation into state-sponsored doping during the 2014 Games in Sochi.

But Povetkin doesn't believe the problem of doping in Russia is as bad as claimed.

"I don't think that our sportsmen in Russia consume all those things they are accused of. It's a bit annoying, to be honest," he said.