Main event time. Welterweight champion Matt Hughes is on the way to staking his claim as the greatest 170-pound fighter in UFC history. He's won 18 of his past 19 fights going back to 2000.

His only loss in that time is to Penn.

Penn dominated Hughes in 2004, scoring one of the most memorable upsets in mixed martial arts history with a submission victory. Penn also marches to the beat of his own drummer and promptly left the promotion in a contract dispute after winning the title. Penn returned this year and lost a split decision to Georges St. Pierre in one of the year's hardest-fought battles. St. Pierre was supposed to get the title shot, but had to pull out due to a groin injury, which enabled Penn to step in as his substitute.

Lights go down and Penn (11-3-1) comes out to the octagon to the Gnarls Barkley song Crazy. Lights go down back down, Hank Williams Jr.'s A Country Boy Can Survive starts, and the two-time NCAA All-American wrestler from Eastern Illinois University strolls down to ringside with the hood of his sweatshirt pulled over his eyes. Huge ovation from the crowd, a sign of respect for one of the game's all-time greats.

Hughes is 32 years old, 5-foot-9 and 170 pounds. Penn is 27, 5-7 and weighed in at 166.5.

Round 1:  Crowd is amped as the combatants circle each other. Hughes grabs BJ's leg, BJ tries to escape, but Hughes runs him back into the fence. Hughes tenaciously clings to Penn's right leg, but Penn won't go down. They continue to cinch each other on the fence. They trade a couple punches and take it back out center octagon. The look of intensity on Hughes' face is something on another level. BJ rocks Hughes with a left, Hughes tries a takedown, but BJ ends up on top. Penn has ridiculous flexibility and has his right leg wrapped around Hughes head. Hughes gets up and kicks Penn away. They trade shots again in center ring. The round is very much still up in the air with under two minutes left. They trade a few jabs. Penn hits Hughes in the eye and referee Big John McCarthy calls timeout. Was that a punch or an eye poke? Or was he pushing Hughes away and accidentally caught him in the eye? The doctor clears Hughes and the fight continues. Hughes locks up Penn on the restart and pushes him against the fence. Huge "BJ" chant in the crowd. Round ends. I am giving round 1 to Penn, but I have to state here I'm not sure what happened with that punch, don't have the benefit of listening to the announcers and it's hard to tell on the big screen replay.

Round 2: Hughes goes for a single leg, but Penn is so slippery. Finally Hughes gets him down, and, uh-oh, Penn is in Matt Hughes ground-and-pound territory on the mat, and that is not a good place to be. "Hughes" chant starts. Hughes hasn't been able to do much, though. They've been on the ground awhile and Hughes has gotten a couple punches in. Penn tries for a submission from a bizarre position and Hughes escapes it. They're still on the ground. Under two minutes left. Hughes hits a couple elbows, but BJ escapes and Penn has his back. The building is absolutely rocking. Penn tries to sink in a choke, but he hits Hughes with an elbow. Now Penn has a choke sunk in with his legs. 30 seconds left in the round. He's got Hughes scissored and is trying to straighten him out with an arm triangle. Hughes somehow survived that and the round comes to a close. That was five of the most intense minutes of action in the history of the sport. I have this 2-0 Penn.

Round 3: Hughes with a couple jabs. They're trading punches. Hughes scores a right-left combo. Still stalking at center octagon. Hughes hits a kick to the midsection. Hughes continuing to irritate Penn with punches, he's clearly adjusted his strategy on the fly and now he's doing damage. They hit the ground with Hughes on top near center octagon. Still struggling for position. Hughes trying to free up his arms, Penn cinching. Hughes lands a series of rights. Hughes gets impeccable position and starts hitting a massive flurry of rights. Literally about 20 punches. Penn still defending. Hughes raining more punches.  Penn tries a knee to the body. More punches ... and referee McCarthy finally stops it at 3:53, as Hughes retains his title in a war. Tremendous, tremendous victory for the greatest welterweight fighter in history in what will go down a one of the year's most memorable fights.