By Simon Austin

Francis fought Klitschko in 1998

Danny Williams could be making a big mistake by fighting WBC champion Vitali Klitschko in December, British heavyweight Julius Francis has warned.

Francis - who has fought both men in the past - says Williams is taking on the fight too soon after his July win over Mike Tyson.

"Fighting Klitschko is a different ball game," Francis told BBC Sport.

"He has a tremendous punch and chin and even Lennox Lewis had trouble with the sheer size of him."

Francis, 40, thinks Williams should have instead opted for a re-match against Tyson.

"Win, lose or draw, Danny would have made millions and still been a world-ranked fighter," Francis said.

"Or he could have gone and got a feel for fighting someone ranked just outside the top 10 in America - he's only fought there three times so far in his career."

Francis knows from personal experience what an awesome proposition Klitschko is. He was beaten in two rounds by the Ukrainian in 1998.

As much as I admire Danny, I have to lean toward Klitschko winning the fight within seven rounds Julius Francis

"He's 6ft 8in but he's not a beanpole, he's a very well-structured and physical man," Francis said.

"The sheer height of him will pose a lot of problems for Danny. To punch up to his head you're going to leave yourself exposed.

"Danny has to work his way inside and really punish Klitschko's body. If he can do that, he's got a really good chance, but he's got to do it early.

"Danny will have to get past that long reach and keep bobbing his head like Tyson used to.

"As much as I admire Danny, I have to lean toward Klitschko winning the fight within seven rounds, he holds too many cards."

And Francis fears defeat could severely dent Williams' confidence and even damage his career.

"We saw the effect when Danny lost to Sinan Samil Sam at the start of 2003. In his next few fights there was something missing from him," Francis said.

"Guys who shouldn't have been able to get near him were able to hit him and hurt him."

And Francis knows from personal experience the damaging effect that taking on the wrong fight at the wrong time can have.

He was beaten in four rounds by John Ruiz - who later went on to become WBA heavyweight champion - in 1994.

"I should never have fought Ruiz when I did, not with the calibre of boxer he was and the people he had been in with," Francis said.

"He'd fought in a much higher class than me and look what he went on to do."