As previously reported on BoxingScene.com, Anthony Joshua's next scheduled opponent Jarrell Miller has returned an "adverse finding" in a test conducted last month by the Voluntary Anti-Doping Association (VADA), according to promoter Eddie Hearn.
Joshua (22-0) is set to defend his WBA, IBF, IBO and WBO heavyweight titles on his American debut against the similarly undefeated Miller at Madison Square Garden on June 1.
But while the 2012 Olympic gold medalist continues preparations for the fight, Hearn - who represents both fighters under his Matchroom banner - revealed he had been informed of an adverse finding from New Yorker Miller.
"We have been informed by VADA that there has been an adverse finding in Jarrell Miller’s sample collected on March 20th, 2019," Hearn wrote on Twitter.
"We are working with all relevant parties and will update with more details soon. AJ's preparation continues for June 1st at MSG."
Former cruiserweight world champion and Sky Sports pundit Johnny Nelson is shocked with the news.
"It's a total shock. If it is true, it is a foolish situation to be in. If he fails a second test he has got to be punished severely. I remember Lennox Lewis boxing Vitali Klitschko. Klitschko was a stand-in and that became a life and death situation. It was a tough, tough fight but Lewis won," Nelson told Sky Sports.
"The [replacement] opponents who come in six weeks before the fight are the hard opponents. These are the ones that you can't get up for, to obsess over. For them, it's a massive opportunity. The name that comes to mind is Kubrat Pulev, who would have fought Joshua before but for injury. That is a strong possibility.
"Then there is the dangerous Luis Ortiz who has lost to Deontay Wilder before. An outside bet is Michael Hunter. There are options out there. But with only six weeks left, anybody who steps in knows they are up against it. Anthony Joshua is very formidable."
Miller (23-0-1) last fought in November, beating Romanian Bogdan Dinu inside four rounds, two months on from Joshua stopping Russia's former world champion Alexander Povetkin at Wembley in seven.