Kubrat Pulev will take on Anthony Joshua either this year or in 2017, says promoter Kalle Sauerland.
The Bulgarian has been named on a three-man shortlist of possible opponents for IBF heavyweight champion Joshua, which also includes mandatory challenger Joseph Parker and Bermane Stiverne.
Joshua is expected to make one more defence of his title before the end of the year after successfully retaining his title with a seventh-round stoppage of Dominic Breazeale in June.
Pulev (23-1 KO12) is just behind Parker in the IBF rankings and his promoter Sauerland says 'The Cobra' could enforce his own shot at the title next year, if he is not selected as Joshua's latest foe.
"I think it's a fight that will happen, whether we agree now to a voluntary or not," Sauerland told Sky Sports. "Pulev is in the No 2 position after Parker, his mandatory.
"The next mandatory will likely be Pulev in 2017, so whether the fight happens now or next year, the fight will happen.
"I think it's a great fight. Obviously two big guys. Joshua has made a storming entrance to the professional ranks, but I think he is still learning on the job, which you can see from his last opponent.
"Pulev is a big step up and it's a good fight, it's a real 50-50 if you ask me."
The 35-year-old has suffered just one defeat, a fifth-round knockout to Wladimir Klitschko in 2014, and comfortably outpointed Dereck Chisora to win the vacant European title in his first fight with new trainer Uli Wegner in May.
Sauerland believes Pulev learned from his solitary loss and could trouble the imposing 6'6" tall Joshua, who has stopped all 17 of his opponents.
"You talk about Pulev's loss to Klitschko, he took the totally wrong strategy that night, everything went wrong.
"But we must not forget that before he went down, he wobbled Klitschko and Klitschko being the long-standing champion, he had the experience to come out of that and put him down.
"Pulev isn't a one-punch fighter, but he's knocked out bigger guys than Joshua. If you look at Dimitrenko and Ustinov for example, they are big, big guys, and he's stopped them.
"It's a real fight, a live fight. Let's see if they want to do it now, or whether they want to wait until next year."