Ruiz Jr, who will be bidding to become Mexico's first heavyweight world champion, replaces Joshua's scheduled opponent Jarrell Miller, who was barred from fighting after failing drugs tests
Jarrel Miller denied boxing license over failed drug test ahead of bout with Great Britain's Anthony Joshua
Jarrell Miller was denied a license to box by the New York State Athletic Commission (NYSAC) over a failed drug test on Wednesday, scuppering his planned 1 June bout with world heavyweight champion Anthony Joshua.
Eddie Hearn says in a Twitter post that Joshua's camp has been informed by the Voluntary Anti-Doping Association that there was an adverse finding in a sample collected from American boxer Jarrell Miller on 20 March
Anthony Joshua vows to 'strip Jarrell Miller of his soul' in world heavyweight bout in USA to defend IBF, WBA and WBO crowns
"I'm going to strip him of his soul in that ring. I'm going to reconstruct his face and his body on June 1," Anthony Joshua said.