"A dream is free. So I can dream. I always allow myself to dream." Francis Ngannou acknowledges he will not be able to answer his critics until he shows how he can box against Tyson Fury; Ngannou is a former UFC champion but boxes for the first time against leading heavyweight Fury

Francis Ngannou is a former UFC heavyweight champion. But the mixed martial artist has never had a professional boxing bout before. His first will be on Saturday in an unlikely 10-rounder with Tyson Fury.

Fury is, of course, the WBC champion and widely regarded as the leading heavyweight in the sport.

In short, it's hard to imagine Ngannou being competitive with Fury. But Ngannou is willing to defy his critics.

"I can't change what people think or how they view it, until I get there and fight and make them take me more seriously," Ngannou told Sky Sports.

"I think the only way to change that is to show how I can fight, how I can box. Because they are right not to believe in something that they haven't seen. And you can't blame them until you show them."

Upsetting Fury would be a "dream" but it's one that he has faith in.

"I beat him," he said. "I'm going to win. A knockout is a part of it."

His vaunted punch power was effective in MMA and he maintains that asset can help him against Fury, even in a boxing match in 10 ounce gloves.

"I might not have that power at the end of the day - but I just believe in it. A dream is free. So I can dream. So I always allow myself to dream," he declared. "You know what other dream I have. To beat Tyson Fury."

That outcome is implausible. But being involved in such an event is a fairy-tale end in itself for a man whose life has taken him down the hardest of paths.

Ngannou worked in a quarry when he was a child. As an immigrant he travelled to France, hoping to become a boxer and spent a period of timeless homeless on the streets of Paris. He converted to MMA which ultimately culminated in his UFC title triumph.

"I think my life experiences have helped me to build my resilience, my determination and that's why I get here today," he said.