Promoter Eddie Hearn has described Kiko Martinez's knockout of Kid Galahad as "the most stunning thing he has ever seen in a boxing ring".
Galahad was the overwhelming favourite with the bookmakers, and the Sheffield fighter looked to be on course for a routine win over the veteran Spaniard.
However, Martinez heavily dropped Galahad at the end of the fifth, before knocking out the IBF featherweight champion with the first punch of the following round.
Speaking after the fight, Hearn said: "I can't believe what I've just seen. It was the most stunning thing I've ever seen in a boxing ring. It was such a one-sided fight. It was a beatdown, a masterclass.
"One punch changes everything. Kiko Martinez has been fighting at the top for 15 years. I knew he would not stop trying. He was completely outclassed by Galahad."