Kell Brook will not commit to his pursuit of Jarrett Hurd until he has received a clear answer from Amir Khan.
Brook described his long-awaited potential clash against Khan as "now or never" after beating Michael Zerafa on Saturday.
That victory earned Brook, a former world welterweight champion, a shot at the WBA super-welterweight title held by Hurd.
Amir has a decision to make - does he want to fight Brook or Crawford?
"Kell has got the opportunity to fight Jarrett Hurd. He will be the mandatory. That could be the next fight for Hurd, or the one after," promoter Eddie Hearn told Sky Sports.
Khan's option to challenge for Terence Crawford's WBO welterweight title has become the latest hurdle in his negotiations to fight Brook.
Hearn, who has held talks with Khan's team this week, said: "Amir has a decision to make - does he want to fight Brook or Crawford?
"Kell did not look at his best so Khan may now fancy that fight."
Khan has previously demanded that Brook cut back to welterweight (10st 7lbs) to agree a fight then commit to a rehydration clause preventing him from gaining more than 10lbs after the weigh-in. Brook, last Friday, weighed-in for his super-welterweight (11st) fight at 10st 10lbs, approximately four pounds light.
"I will go to welterweight, I will do the rehydration [clause]," Brook said on Saturday.
Hearn added: "Kell has got to decide, if he doesn't get Khan, does he move back to 147lbs and fight the likes of Shawn Porter, Danny Garcia or Jessie Vargas?
"In the next week, Amir will make up his mind. Then we'll know where we are going."
Brook, post-fight on Saturday, stressed the need to fight Khan next because his rival's contract with their mutual promoter Hearn is due to expire.
"He's got one fight left with Eddie," Brook said. "The time for the fight is now. I'm ready to go. It's now or never.
"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."
Unbeaten American Hurd, meanwhile, holds IBF and WBA gold at super-welterweight.
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