Following his third loss in four fights, the man who burst onto the heavyweight scene in such explosive style two decades ago declared that his career in the ring was over.

"This is it. I'm finished. It's just not in my heart," the 38-year-old Tyson told a post-fight news conference.

"I'm just not interested in fighting anymore."

Similar to his recent knockout defeats to Britons Lennox Lewis and Danny Williams, the end of the bout came swiftly and surprisingly.

After starting brightly, a clearly exhausted Tyson head-butted McBride in the first minute of the sixth round, delivering a nasty cut over the Irishman's left eye.

With blood gushing down his face, McBride continued to work inside, pushing the flagging Tyson to the canvas as the round ended.

Appearing unhurt but short of energy, Tyson staggered to his corner and slumped on his stool where his cornermen requested referee Joe Cortez to stop what could be his last fight.