Weidman had unanimously taken the first round, and Romero the second. The eventual result figured to have a major impact on the 185-pound division. Commentator Joe Rogan remarked, "This is shaping up to be very interesting."
And then just like that, it was over. Weidman dropped into a single-leg takedown and was met perfectly by a Romero flying knee. Romero leaped into the knee with such force that he was nearly thrown into a full somersault from the impact.
It was an instant knockout for Romero, in his only appearance of 2016. And it came against a former champion who was fighting in his home state.
"I knew it was going to happen in the fight," Romero told ESPN.com. "I actually kept baiting him with my front leg. My manager, Abraham Kawa, saw me practicing the knee two days before the fight while I was hitting pads and told me, 'If you connect this in the fight, it will be sweet dreams for Chris.'
"I don't think 'timing' was the best way to describe it. It was more like a feeling. My instincts took over."
Weidman crumpled to the floor. He sat up moments later, blood pouring down the side of his face. He would later receive 10 stitches, including three to repair an injury caused by his own knee hitting his face as he fell straight down.
Romero celebrated by leaping out of the Octagon and marching around the perimeter like a wind-up toy soldier. It was one of the most vicious, opportunistic, significant finishes of 2016 and is ESPN's choice for knockout of the year.
"Every knockout or finish is satisfying, but to do that to a former champion and a tremendous fighter like Chris is good," said Romero, who has 10 career knockouts. "The most satisfying will be when I get the KO that leads to [UFC president] Dana White wrapping the belt around my waist."