In one of the crazier fights in recent memory, Mitrione (12-5) knocked out Emelianenko at 1:14 of the opening round inside Madison Square Garden -- just moments after both hit the deck from simultaneous right hands.
Mitrione, of Indianapolis, dropped to his seat but looked clear-eyed and quickly scrambled to his feet. Emelianenko (36-5) bent forward and tried to grab hold of Mitrione's lower body to slow him down. Mitrione postured, landed a hard right hand and then followed up with several more shots to earn the knockout.
"It's crazy. Right in the middle of the fight, he's so smart, he started looking at my hips and watching my feet," Mitrione said. "So I switched it up with him, and maybe I confused him. I engaged when he engaged."
It was a satisfying result to a fight that was supposed to happen in February. Mitrione was forced to withdraw from the original date just hours before the event due to kidney stones.
Rather than agree to a change in opponent, Emelianenko, of Russia, elected to reschedule the Mitrione bout. Before Saturday, Emelianenko, 40, hadn't fought in the U.S. since 2011.
"He's not arguably the great heavyweight of all time, he is the greatest heavyweight of all time," Mitrione said.
Immediately after the bout, he encouraged fans to make a donation to the family of Tim Hague, a veteran mixed martial artist who died from injuries suffered in a pro boxing match earlier this month at age 34.