"UFC and I didn't come to terms," Poirier told ESPN. "I will not be fighting on Oct. 24."
Poirier recently traveled from his home in Lafayette, Louisiana, to South Florida to begin his training camp in hopes of a deal being struck. But he said Thursday that he will now be returning home next week and is unclear whether the fight will be salvaged for a later date.
On Wednesday, Poirier told ESPN he would be willing to take the fight if the money was right.
"I just need to be compensated if they want this fight," he said. "Simple as that.
"I'm a prize fighter and the prize needs to be right."
In addition to it being a big fight, sources say extra stakes were attached to it: The UFC had discussed a scenario where if Gaethje withdrew from the main event, Ferguson would have replaced him versus Nurmagomedov. However, if Nurmagomedov pulled out, Poirier would have replaced him versus Gaethje. The stipulation made sense considering Nurmagomedov-Ferguson is a fight the UFC has tried to book five times before to no avail, and Poirier has a win over Gaethje.
According to sources close to Ferguson, "El Cucuy" had verbally agreed to the fight but not signed yet, either. Ferguson's team declined to comment on this latest development when contacted by ESPN.
In late August, UFC president Dana White said the promotion was "probably" going to book Ferguson vs. Poirier next, but neither the promotion nor White has publicly discussed the status of the fight since then.
Poirier (26-6, 1 NC) is coming off a win over Dan Hooker in June. He has won five of his last six fights, with his lone loss coming against lightweight champion Nurmagomedov last year.
Ferguson (25-4) had his 12-fight winning streak snapped in May by Gaethje.