American debut is in threat after opponent Jarrell ‘Big Baby’ Miller was reported to have tested positive to drugs test.
Joshua was planned to fight Miller at New York’s Madison Square Garden on June 1.
The revelation of a negative finding for performance enhancing drugs on March 20 almost certainly leaves promoter Eddie Hearn scrambling to find a replacement.
However, the 30-year old Miller failed drug test for muscle growth substance GW1516, a second sample may be be tested again.
The saving grace for the Joshua camp is that there is still six weeks to go, which should allow time to find another heavyweight.