However Dagenham-born Mitchelll, who is unbeaten in 31 fights, could end up fighting for the full WBO crown, with current champion Juan Manuel Marquez expected to vacate.
“I grew up watching West Ham play and I still can’t believe I’m going to be fighting there,” said Mitchell.
On the same night Amir Khan will be defending his WBA light-welterweight title having his first bout in the United States when he takes on Paulie Malignaggi at Madison Square Gardens.
The event at Upton Park on May 15 is billed as the biggest of its kind since Joe Calzaghe’s super-middleweight unification fight against Mikkel Kessler at Cardiff’s Millennium Stadium in 2007.
Mitchell, 25, knocked out Ignacio Mendoza at Wembley in February to set up the bout, having previously beaten Colombian Breidis Prescott, who had knocked out Khan in the first round.
Katsidis was defeated by former World Champions Joel Casamayor and Juan Diaz in 2008, but then went on to beat former two-weight world champion Jesus Chavez last April, claiming the WBO interim belt from Vicente Escobedo last September.
On fighting in front of a East London crowd Mitchell said: “The fans in the East End are very special people, and to get the opportunity to fight in front of them is a dream come true.”
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BIOGRAPHY: Cesc Fabregas