WBN has been informed by more than one person very close to the fight that Brook has been nursing an ankle injury for the past couple of weeks.
Eddie Hearn has publicly stated doctors would assess brook, but WBN has now been informed Brook will be unable to compete on the Dillian Whyte v Joseph Parker undercard.
Matchroom is said to find a late replacement contest to fill the void as Brook contemplates another lengthy absence.
WBN understands Brook could be out until November with the ailment, which will also set back his hopes of a meeting with Amir Khan over the next few months.
With just two weeks to go until the O2 Arena show in London, it’s a big blow for Hearn, who is hoping to make a success of heavyweight Whyte’s first Pay-Per-View headliner.
Whyte is being pushed as a possible opponent for world champion Anthony Joshua at Wembley in April after WBC title-holder Deontay Wilder cooled off his interest in unification with the top division king.
Wilder wanted a meeting this year, whilst Joshua and Hearn had other plans in the form of a mandatory defense against Alexander Povetkin.
A win for Whyte against Parker would see ‘The Bodysnatcher’ in a prime position to step in should Wilder decide against renegotiating with Joshua and his team for the spring.
For Brook, his bout with Brandon Cook’s cancellation means ‘The Special One’ has fought just twice in two years and won only one encounter since a March 2016 triumph over Kevin Bizier.
After signing up to the World Boxing Council Clean Boxing Program after being stripped of his Silver belt due to non-compliance, Brook was hoping to land a world title shot at Jermell Charlo or Jarrett Hurd at the end of 2018.
Sadly, those plans are now set to go out of the window.
Phil Jay is Editor of World Boxing News. Follow on Twitter @PhilDJay