By Adrian Warren

Alex Leapai's greatest domestic rival Lucas Browne gives him a puncher's chance of dethroning world champion Wladimir Klitschko on one of the biggest days in Australian heavyweight boxing history.

Leapai and Browne, who are ranked first and second respectively in Australia, will both be fighting in Europe on Saturday night (Sunday am AEST).

While Leapai challenges quadruple world title holder Klitschko in Oberhausen, Germany, Browne will fight Canada's Eric Martel Bahoeli in Sheffield England for the vacant Commonwealth and WBC Eurasian Pacific Boxing Council titles.

No Australian has held the world heavyweight title and it's believed the last Australian to hold the Commonwealth crown was West Indian-born Peter Jackson in 1892.

But rarely has Australia had two world-rated heavyweights at the same time - both of them fearsome punchers.

Leapai has 24 KOs in his 30 wins while 17 of Browne's 19 victories have come inside the distance.

Unbeaten professional "Big Daddy" Browne, a 193cm tall former cage-fighter who switched to boxing in 2009, is favoured to win his bout.

Leapai will start a vast underdog against Klitschko who has won his last 19 bouts stretching back over 10 years.

"Alex has a puncher's chance. He doesn't have the skills to beat him," Browne told AAP.

"In saying that, I congratulate Alex on an awesome career thus far and wish him luck."

Asked if he would like to fight Leapai in the future Browne said: "I would love to fight Alex and once and for all sort out who the best in Oz is."

Browne is rated 11th by the WBC and 15th by both the WBA and IBF.

"The fight is for both the Commonwealth title as well as a regional WBC title so (a win) will help my rankings a great deal," said Browne, who has only seen YouTube footage of Bahoeli, who has a record of 10-3 (7 KOs).