Khabib Nurmagomedov is held back outside of the cage after fighting Conor McGregor. (John Locher)

It should’ve been a moment of triumph for Khabib Nurmagomedov. The 30-year-old Russian dominated Conor McGregor, forcing him to submit at 3:03 in the fourth round via neck crank to retain his UFC lightweight championship Saturday night at T-Mobile Arena in Las Vegas.

But then Nurmagomedov climbed the cage and charged a member of McGregor’s team. And what should have been a banner night for the UFC and its lightweight champion turned into bedlam.

Nurmagomedov went after McGregor’s jiu-jitsu coach, Dillon Danis, which triggered a chaotic post-fight scene. Several members of Nurmagamedov’s team then entered the cage as security tried to intervene. And one of the champion’s team members punched an unsuspecting McGregor.

Security personnel eventually got some control over the situation, and both fighters were escorted out. Nurmagomedov left to massive boos from the pro-McGregor crowd, as several fans threw drinks at the Russian.

The incident marred a superb performance from Nurmagomedov (27-0-0). He got the fight to the ground early in the opening round, and sapped McGregor of much of his strength by maintaining top position throughout the frame. The champion nearly finished the fight in the second round with excellent ground and pound, but McGregor (21-4-0) survived and rallied to stabilize the contest in the third.

Nurmagomedov was able to finish it off in round four. After a takedown one minute in, Nurmagomedov took control and eventually got McGregor to tap out via neck crank.

Because of the surreal aftermath, though, there are more questions than answers coming out of UFC 229. A suspension is almost certain. But will UFC President Dana White strip the champion of his belt? And what are the legal ramifications? Will Nurmagomedov have his U.S. visa revoked? Will he be arrested?

White said three Nurmagomedov team members have been arrested.

As for the UFC’s biggest star, this was a truly lopsided defeat. But he’ll certainly have the fans in his corner after being attacked in the octagon post-fight.

It was a brilliant fight marred by a horrific incident.

— Main card: Khabib Nurmagomedov (27-0-0) def. Conor McGregor (21-4-0) with rear naked choke in lightweight championship (3:03 of round 4)

Round 1: The pro-McGregor crowd roars, Herb Dean gives the signal, and we are underway. McGregor opens by looking to press the pace, but this fight is quickly on the ground — right where Nurmagamedov wants it. McGregor is holding his own, but Nurmagomedov completes the takedown and he’s got the challenger’s legs locked up. The crowd boos, as this is not the action they wanted to see. But Nurmagomedov is following the blueprint. McGregor simply cannot work his way up. The Irishman lands a couple of soft shots from his back, but this round has belonged fully to the champion. 10-9 Nurmagomedov.

Round 2: Nurmagomedov lands a monster right hand early in the second! That shot was right on the money. And now, the champion goes in for the takedown. He’s got top position and he’s fully in control. Some solid ground and pound here midway through the round. McGregor has absolutely no answers. Now, the Russian is landing some heavy, heavy shots with McGregor still on the ground. Referee Herb Dean is looking closely. How long can he let this go on? McGregor is allowed to fight through. With 45 seconds remaining in the round, the Irishman works back to his feet. He makes it out of the second, but barely. This was a dominant round, a 10-8 on this card. 20-17 Nurmagomedov.

Round 3: Did Nurmagomedov expend too much energy trying to close the show? For the first time in the match, the two fighters have spent an extended period of time on their feet. McGregor appears to have an opportunity to land his left, but he just can’t summon the energy he needs to throw with authority. With just over a minute left in the round, Khabib goes for the takedown, but McGregor remains on his feet. Very close round. McGregor has landed a few more significant strikes, and gets the nod in the third as a result. 29-27 Nurmagomedov.

Round 4: The first minute of the round is controlled by McGregor in the center of the cage. But the champion goes in for the takedown and is successful. (He’s 4-for-7 on takedown attempts thus far.) The crowd boos again, as they sense their man’s in trouble. Big trouble. And here goes Nurmagomedov for the rear naked choke. And it’s over! Khabib Nurmagomedov retains his UFC lightweight championship.

Aftermath: And Nurmagomedov jumps out of the octagon and attacks McGregor’s jiu-jitsu coach Dillon Danis! Security tries to step in during the chaos. A member of Nurmagomedov’s team attacked McGregor in the octagon. Dana White is in the octagon now talking to McGregor and trying to restore calm. This is a wild scene.

McGregor leaves the octagon, as Nevada State Athletic Commission Executive Director Bob Bennett enters and tries to get to the bottom of what transpired. UFC President Dana White tells Nurmagomedov that he fears that the crowd will throw objects at the cage if he puts the belt on him. Nuragomedov heeds the warning and leaves. Indeed, as White feared, the fans do throw beer on the champion. Ring announcer Bruce Buffer makes it official after both fighters are gone. Your winner by submission at 3:03 of the fourth round by neck crank: Khabib Nurmagomedov.

— Tony Ferguson (24-3-0) def. Anthony Pettis (21-8-0) by technical knockout (5:00 of round two)

What a table-setter for the main event. After an excellent first round, in which Ferguson applied effective pressure while Pettis landed some solid counters, the two lightweights absolutely went at it in the second. Pettis landed a perfect right hand to put Ferguson in trouble, and just seconds later, the fight was on the ground and both men were bleeding profusely. The ringside doctor examined Pettis, but allowed the action to continue. About halfway through the round, Ferguson began to dominate with a series of terrific strikes. Pettis was still landing some, but Ferguson nearly finished matters with seconds left in the frame.

But as it turned out, Pettis had broken his right hand while throwing a punch, and cornerman Duke Roufus didn’t send his fighter out for the final round.

The exciting victory should position Ferguson, the No. 2 ranked lightweight, to face the winner of Nurmagomedov-McGregor. Ferguson called out McGregor in the ring afterward. That one would be a thriller.

— Dominick Reyes (10-0-0) def. Ovince Saint Preux (23-12-0) via unanimous decision

— Derrick Lewis (21-5-0) def. Alexander Volkov (29-7-0) by technical knockout (4:49 of round three)

Lewis, the No. 2 ranked heavyweight, appeared to be on his way to a unanimous decision defeat. But Lewis landed a stunning overhand right with time running out in the final round. The blow dropped Volkov, and Lewis finished him off with ground and pound — as referee Herb Dean stopped the match with just 11 seconds remaining, to the delight of the capacity T-Mobile Arena crowd.

— Michelle Waterson (16-6-0) def. Felice Herrig (14-8-0) by unanimous decision

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