A brilliantly contested lightweight title fight between Khabib Nurmagomedov and Conor McGregor was instantly marred by an ugly incident inside and outside of the Octagon on Saturday night at T-Mobile Arena.

Nurmagomedov (27-0) defended his 155-pound championship by submitting McGregor (21-4) at 3:03 of the fourth round via rear-naked choke. Immediately after the bout, Nurmagomedov jumped over the Octagon and got involved in a short brawl with members of McGregor’s corner.

Moments later, an unidentified man jumped into the Octagon and began throwing punches at McGregor, who was still recovering from the contest. The events made a mockery of what was otherwise a hard-fought, back-and-forth championship fight at the highest level.

Nurmagomedov, of Dagestan, tried to take McGregor down in the opening minute of the fight. He managed to get him to a seated position on the floor, but McGregor did well stalling him there and landed several elbows to the side of his head as they jostled for position.

In a shocking moment, Nurmagomedov briefly dropped McGregor with a right hand early in the second round. As McGregor scrambled to get back to his feet, Nurmagomedov launched into a flying knee attempt and then used the opportunity to take him down. Nurmagomedov spent the majority of the round in top position, working ground and pound and looking for a kimura.

McGregor, of Dublin, stuffed Nurmagomedov’s early attempts to get it to the ground in the third, and went to work with his offense. He scored good knees and punches to the body after a stuffed attempt, and popped Nurmagomedov’s head back with an uppercut. 

Entering the fourth round, McGregor was bleeding from a small cut near his left eye. He looked tired, and Nurmagomedov executed an outside trip to get him to the floor. From there, it was a familiar sight, as Nurmagomedov did what he has done so often: passed guard, moved into side mount and eventually got the choke.

The fight was the culmination of a rivalry that has been brewing for several years. It hit a boiling point in April when McGregor attacked a bus Nurmagomedov was riding in at Barclays Center. Both men said they would not respect each other after the fight, regardless of the outcome.

It was McGregor’s first bout since he won the lightweight championship in November 2016. He fought Floyd Mayweather in a boxing match in August 2017, and the UFC stripped him of his belt for inactivity in April.

-ESPN