David Haye could fight Vitali Klitschko this summer with reports suggesting brother Wladimir is struggling for fitness.
Haye's manager Adam Booth is still in talks with opposite number Bernd Boente finalise details of the Briton's heavyweight unification battle with Wladimir, which is likely to take place on July 2.
But with Wladimir still not fully recovered from the stomach muscle injury that reportedly kept him from defending his WBA and IBF titles against Dereck Chisora on two occasions, elder brother Vitali could step in.
Boente said on Sunday that Vitali will be fighting again in June or July after the latest defence of his WBC strap against Odlanier Solis on Saturday ended with the Cuban exile quitting after one round with a badly injured knee.
And Booth told the Guardian that deadlines are in place to settle not only the date and venue of the fight, but also Haye's opponent.
"Third week of April we will make an announcement," Booth said. "By the first week of May, Wladimir will have to tell us if he is fit to fight."
And while three German football stadiums are leading the race to host the big fight, it appears that other European cities are also in the running, including Monte Carlo.