Joshua suffered the first defeat of his professional career, being knocked to the cancas four times in a one-sided upset on his debut on American soil at Madison Square Garden in New York on Saturday night.
Referee Mike Griffin eventually waved it off in the seventh when, after returning to his feet for the fourth time – the two knockdowns followed two similarly hurtful ones in the third, which came after Ruiz Jr’s only knockdown – he was no longer able to defend himself.
Given the nature of the defeat a rematch was always likely with Hearn revealing the move officially on Tuesday afternoon.
“After meetings with AJ, Rob McCracken and the management team in NY, we have today triggered the contracted rematch clause with Andy Ruiz Jnr,” he said.
“The fight will take place in Nov/Dec at a venue to be confirmed shortly.”
Now former world champion Joshua confirmed his desire for a rematch almost immediately after the fight.
“Look out for the end of the year, and what’s next,” said Joshua. “It’s an upset, it’s unexpected. I was the favourite. One shot hit me on the top of the dome and rattled me a bit. I tried to stay in there a few more rounds but the better man won.
“I don’t underestimate anyone. He’s a decent puncher, a decent fighter. He was the better man.
“I’ll tidy up, brush off the cobwebs and go again. But it’s a minor setback.
“Trust me, where I was at in life, I’ve dealt with more s*** than this, with some real big losses, and bounced back.