David Haye returns to the boxing ring for the first time in over three and a half years when he fights Mark de Mori at London's 02 Arena on Saturday.

The heavyweight has made no secret of his desire to win another world title, to challenge WBO, IBO and WBA champion Tyson Fury and to fight the promising Anthony Joshua, but in Australia's De Mori he is returning against the most over-matched opponent of his professional career.

As is so often the case when a fighter makes his comeback, the outcome of Saturday's fight will be decided by how much Haye still has, as opposed to anything De Mori is likely to be able to challenge him with.

When he last fought, in July 2012 when stopping Dereck Chisora in five rounds, the now-35-year-old remained the fastest and most mobile fighter in his division and showed few of the physical signs of wear and tear that affect almost every fighter who reaches the very top. He had lost twice, without ever taking a true beating, and retained the reflexes that inspired the explosive style which was such a strength.

Since then, however, because of injuries he has withdrawn from two scheduled fights with Fury and another with Manuel Charr, most recently in November 2013 because of a shoulder condition that threatened his career.

It is unlikely the reflexes which gave him such a reliable defence and lethal offence remain, and his previous speed will also be undermined by him weighing in at a career-high 16st 3lbs. Not that you would know it to hear him speak.

"It's the unknown because nobody knows what I've got left, except me," he said.

"I believe I know what I've got but until I get in the ring and prove it, it's just me being confident. I've got everything I used to have and then some. I've got experience now.

"People are saying this will be the tricky one, the first fight back is the tricky one. Is the opponent too tough? Is he not tough enough? You don't want somebody who will get knocked out by the first punch but you do you want him to be there for 10 rounds?"

The reality is that even if Haye has significantly declined, it would come as a huge shock for De Mori to last anywhere near 10 rounds. At 6ft 2ins he is an inch shorter than Haye, and on Friday tipped the scales at 17st 5lbs.

A degree of ring rust is inevitable, and Haye may also struggle to find his timing, but a more interesting test of his progress may come in how he works with Shane McGuigan, who has succeeded the respected Adam Booth as his trainer.

"He's seven or eight years younger than me but you'd never know that," Haye said.

"I've been really impressed by what he did and watching (IBF super bantamweight champion Carl) Frampton was one of the main reasons I sought Shane out because I liked what he did, the rhythm, the patience, the punch variety.

"It's a lot of trial and error but that was done months ago. We know what works now.

"I definitely feel that I'm healthy enough to do it.

"It would be a waste sitting around not competing and watching the other guys come through when I believe I'm better than them. I believe I'm the best fighter on the planet but there's a difference between saying it and doing it.

"I just want an opportunity to show it."