LAS VEGAS -- Deontay Wilder said over and over that his rematch with Luis "King Kong" Ortiz would end in a knockout and he advised all who would be watching not to go to the bathroom or to get a snack or to check their cell phone because it could come at any moment.

And it sure did.

Ortiz seemed to be soundly outboxing Wilder until he crushed him with one devastating right hand to the forehead in the seventh round to retain his heavyweight world title for the 10th time on Saturday night at the MGM Grand Garden Arena.

The smashing victory was the final hurdle to a rematch between Wilder and lineal champion Tyson Fury, who are penciled in for the main event of a joint pay-per-view between ESPN and Fox on Feb. 22 at the MGM Grand Garden Arena.

Wilder, who was boxing at the MGM Grand for the first time since he won his world title by one-sided decision against Bermane Stiverne in January 2015, took the fight with Ortiz even though he already had the rematch with Fury signed.

Given their tremendous power, Wilder and Ortiz began at a very cautious pace reminiscent of their first fight, but Ortiz did land a solid straight left hand. He also suffered a small cut in the corner of his right eye from what appeared to be an accidental head-butt.

Wilder (42-0-1, 41 KOs), 34, of Tuscaloosa, Alabama, barely threw or landed anything in the early going as he looked for a spot to launch his powerful right hand.

The slower pace favored the older Ortiz, but Wilder landed a solid right hand in the third round that knocked Ortiz briefly off balance in a round he otherwise got the better of.

Ortiz launched two hard left hands early in the fourth round that backed Wilder up and when he landed another shot, Wilder responded by beating his chest.

Wilder seemed reluctant to throw his right hand much and took several 1-2 combinations from Ortiz during the middle rounds. But in the seventh round, he flicked out a jab and came behind with the clean right hand that hammered Ortiz and dropped him hard. He struggled to gather himself and could not as referee Kenny Bayless counted him out at 2 minutes, 51 seconds.

The fight was a rematch of their memorable see-saw battle on March 3, 2018, in Brooklyn, New York, where they fought a contender for fight of the year in which Wilder dropped Ortiz in the fifth round, barely survived a massive onslaught of blows over the final 45 seconds of the seventh round and rallied to score a highlight-reel knockout in the 10th round of a fight Wilder led 85-84 on all three scorecards at the time of the knockout.

Ortiz (31-2, 26 KOs), a 40-year-old southpaw, a Cuban defector fighting out of Miami, was bidding to become the first Cuban to win a heavyweight title.