On Saturday night in Sheffield, former welterweight champion Kell Brook (38-2, 26 KOs) picked up an uninspiring twelve round decision win over Michael Zerafa.
Afterwards, Brook called for a fight with his domestic rival, Amir Khan.
Promoter Eddie Hearn is hoping to match the two boxers in the first quarter of 2019.
And Hearn's plan since the start of the year was to use 2018 to slowly build a Khan-Brook showdown.
Khan had signed a three fight deal with Hearn in early 2018. There is one fight remaining on that agreement.
That deal is now in jeopardy, after Khan received an offer of a $5 million guarantee for a fight with WBO welterweight champion Terence Crawford on March 23 at Madison Square Garden in New York City.
Khan has openly stated that he's very interested in taking that fight - and more interested in Crawford than he is in facing Brook.
He believes that win or lose against Crawford, the fight with Brook will "always be there."
Brook disagrees, and says he won't entertain a beaten Khan.
"Let's just make the fight. I've agreed to all his demands, I'm not holding this fight up. It's down to him. He's got one fight left with Eddie (Hearn). The time for the fight is now. I'm ready to go. It's now or never," Brook told Sky Sports.
"He's saying that fight's always going to be there - it's not always going to be there. I'm trying my best to make it happen for the fans while we're together under the same [Matchroom Boxing] umbrella.
"If he decides to go a different way, it won't be there again, because I'm going for the big boys who want to come and fight. Then when he comes crawling to me after he gets beat, it won't happen. I'm telling you now, so the fans know: it has to happen now."