Deontay Wilder is in "ongoing" talks to fight Francis Ngannou - and the pair could collide in a never-seen-before set of rules.
Ngannou walked out on the UFC to sign with rivals the Professional Fighters League, who gave him the green light to also pursue boxing.
The Cameroonian was in negotiations to fight Wilder but he instead agreed a deal with Tyson Fury for a crossover clash in Saudi Arabia.
Ngannou, 37, amazingly dropped Fury, 35, but was controversially beaten by split-decision on the scorecards.
The ex-UFC champion now wants to wait for a rematch after Fury's undisputed showdown with Oleksandr Usyk, 36, on February 17.
So it paves the way for Ngannou to make a return to MMA in his next fight, also marking his debut in the PFL.
PFL CEO Peter Murray has named Wilder as a potential opponent and confirmed talks will continue with the American boxer.
Murray said as cited by Sports Central: "Absolutely, ongoing. I'm going to see Deontay next week and we want the four-ounce gloves on him with Francis in the cage."
Wilder has in the past called for a two-fight deal with Ngannou, to meet in the ring and cage.
But Murray has teased that a mixed-rules bout could be agreed in a bid to level up the playing field, a hybrid never before seen.
He said: "We're working through those details. "I mean it's a fight that Francis wants, it's a fight we believe Deontay wants and we're focussed on putting it together."
Wilder, 38, first returns on December 23 in Saudi Arabia against New Zealander Joseph Parker, 31.
Anthony Joshua, 34, is also in action that night against Otto Wallin, 32, in the hopes of building towards a blockbuster with Wilder next year.
But Murray still believes Ngannou could face Wilder in his next bout despite the mega-money boxing moves.
He said: "I think as relates to the next fight, yeah a Wilder is much more likely. That is our goal."