Undefeated welterweight Brook had been due to face IBF champ Alexander on February 23, but his US opponent had to postpone due to a bicep injury.
An ankle injury to Brook had already scuppered the original bout, which had been scheduled for January 19, and the Briton admitted that he is now unsure of what the future holds, particularly after pound-for-pound king Floyd Mayweather went public with his desire to fight Alexander.
“I still don’t know — I’m still in limbo with it all,” Brook said. “I’m absolutely gutted. I’ve been training for 13 weeks, then I heard from my family. Finding out the news, I can’t put into words how devastated I am.
“But I’ve got to be professional about it. I’ve got to keep ticking over, keep my mind on it and wait to hear from them.”