Deontay Wilder needed to knock out Luis Ortiz to maintain his unbeaten professional record - with the scorecards showing he was heavily behind in the fight.
Heavyweight champion Wilder was well behind on all three scorecards after six rounds, after Cuban Ortiz had boxed superbly to put himself in the box seat for a shock.
But 'The Bronze Bomber' produced an incredible punch to knock out his rival in the seventh round - with 40-year-old Ortiz unable to get back to his feet before the referee had finished his count.
That may have set him on a collision course with a Tyson Fury rematch, but it didn't hide his six rounds of being bettered - with the judges giving scores of 56-58, 55-59, and 55-59 in Ortiz's favour.
Eric Cheek had Ortiz up by two points having given him the third, fourth and fifth rounds, with Wilder winning the first.
Dave Moretti adjudged Ortiz to have an even greater margin, having handed him the first five rounds before Wilder claimed the sixth.
And Steve Weisfeld scored identically to Moretti.
In the 'explain deduction of points or comments' section was written: "Ortiz scalp laceration head butt first round."
Wilder admitted Ortiz was "very crafty" and "moves strategically" before confirming that British superstar Fury is next on his to-do list.
“With Ortiz, you can see why no heavyweight wants to fight him, he’s very crafty and he moves strategically," said Wilder.
“I had to measure him in certain places. Some people say I can’t fight on my back foot but that’s my speciality. I had to go back and forward, my intellect is very good in the ring.
“I finally found my measurement, I saw the shot and I took it. He’s one of the best in the world, you've got to give him that.
“Next is Tyson Fury, that is settled for February and then I want a unification fight.”
Ortiz added: “This is boxing, I told everybody that it was going to be him or me and that it wasn't going to go 12 rounds.
“I was clear-headed. When he said seven I was trying to get up but the count was maybe quicker than I thought."
