Given that Amir Khan has been out of the ring for almost two years, he must have had a lot of time to reflect on what brought his career to a standstill.

The 31-year-old is making his return against Phil Lo Greco in Liverpool next weekend, with the ultimate aim of earning a fight against Kell Brook or Manny Pacquaio.

Before he can earn a shot at any such fights, the former Olympic silver medallist has some making up to do - not least because in his last outing, he was badly knocked out by Saul Alvarez.

That must be a particularly bitter pill to swallow, with the Mexican having been temporarily suspended after testing positive in two separate drugs tests earlier this year.

'Canelo' was due to fight Gennady Golovkin before the bout was cancelled in light of the ongoing investigation.

If he is innocent, it will be difficult for him to recover his reputation regardless, as it is a cloud that will always hang over him.

Indeed, in an interview with the Telegraph, Khan has raised fresh doubts about his old rival's integrity, questioning whether the Mexican was even clean in 2016.

Khan queries Canelo 

“I’m not saying he was on something when I fought him, but you could see he’d put on a lot of weight," Khan said.

“I hope he was clean when I fought him, he’s always going to say he was clean. Only God knows. But he got so big, so quick after the weigh-in. He put on over 35 pounds of weight. I thought there must be something wrong there. I could see how strong he was when I fought him."

That's a huge statement to make and one which it will be very difficult to prove, though Khan has teetered on the side of caution by avoiding calling out Canelo directly.

There is little sympathy, though, for the disgraced 27-year-old and the British star insists his punishment must set a precedent to others in the sport.

“He’s been caught taking drugs which is illegal. He's a big name in the sport, and I think that he definitely needs to be taught a lesson," Khan added.

"Otherwise all fighters will think it’s okay. There’s a saying: once a cheat, always a cheat. I’ve never taken drugs in my life and never will, I want to win fights on my own skills and my own abilities. But when people need that bit of advantage, it’s unfair.”

What do you make of Khan's comments? Have your say in the comments.