This is the live blog for Raul Rosas Jr. vs. Raoni Barcelos, the bantamweight main event for Saturday's UFC Vegas 121 fight card at the Meta APEX in Las Vegas.

Rosas Jr., the youngest athlete in UFC history to earn a contract when he got a victory on Contender Series at just 17 years of age, competes in his first octagon main event. Now 21, Rosas enters the bout on a five-fight win streak, including a decision victory against Rob Font at UFC 326 in March. “El Niña Problema†is 6-1 overall in the UFC with the lone loss coming to Christian Rodriguez at UFC 287 in April 2023.

Barcelos is also entering his first UFC main event on a five-fight win streak, including handing Payton Talbott his lone octagon defeat. The 39-year-old's impressive run also includes wins over Montel Jackson, Ricky Simon and former champion Cody Garbrandt.

Check out the UFC Vegas 121 live blog below.

Well, that co-main event was so bad that Paul Felder just kinda went after Ailin Perez over it.

Hopefully this main event will be better.

Chito Vera in Raul Rosas' corner. That's a fun wrinkle. Both men looking ready. Barcelos looking like a weathered old man who will beat the heck out of any upstart young whippersnappers. Let's see if he can do just that to Rosas.

Oh, the screen tells us that this is the largest age gap in a UFC fight ever, at 17 years. That's something interesting!

Both men out in orthodox and Rosas looks like the bigger man, for sure. He's switching stances and probing with calf kicks early. Barcelos is holding his ground and looking for big uppercuts and right hands. Rosas just slips back whenever Barcelos throws, at least early on.

So Barcelos goes to the body and that's a good shot. And it clearly inspired Rosas, because he got a bit wild out of nowhere. Hard pressure from Rosas and a good right hand. Collision, grappling, break, and Rosas eats a right hand as well. Rosas feeling confident in his hands now and he's throwing sharp hooks in combination. A few land and I think Barcelos has a cut on his nose now. Oh he definitely does, and he fires back, then changes levels to his own takedown and gets it.

Rosas throwing hammerfists from his back to force Barcelos to move and then scrambles up. High pace to start this one. They go right back to it, colliding and throwing shots in the phone booth. This is mostly brawling, and it's very fun. Rosas wearing damage well, while Barcelos showing some major swelling on his face, and the blood. But Barcelos starts coming on strong with a minute left.

Rosas ssticking right there in the pocket with him and then punching back in combination. Barcelos showing slightly more craft in these exchanges, but Rosas' willingness to mix it up is doing well for him. That was a very competitive round, but I do wonder if Rosas can keep up this pace.

MMA Fighting scores the round 10-9 Rosas.

Barcelos out to the center to start and lands early, but Rosas fires a sharp left hand. And then Rosas eats a jab while stepping in and he backs off. That caught him in a tough spot. Rosas goes to the calf while Barcelos misses a big uppercut. Rosas back to the calf, and he needs that for a war of attrition. Barcelos, meanwhile, keeps tagging the body during his combinations.

Rosas comes on strong though, charging forward with aggression. Rosas eats one though and he's now bleeding, I think from the bridge of the nose. Another uppercut from Barcelos, and he's starting to get a rhythm as Rosas seems to be slowing. then Barcelos grabs a snatch single and gets Rosas down, but he's right back up.

Rosas still very committed to his shots, but there are fewer of them. He's definitely slowing a bit, and the speed is certainly dropping off. Barcelos is slipping more punches now, and landing more. But Rosas just keeps putting volume down and cracks Barcelos. That gives him a surge of adrenaline and he charges in but Barcelos fends him off.

Big right hand from Barcelos and then into a takedown that he gets with ease. Rosas turtles and Barcelos tries to take the back, but Rosas stands. Barcelos holding this rear waistlock though, and tries to sneak the choke in. Rosas turns and they start hockey fighting along the fence. This is a crazy pace. And Barcelos keeps going to the body. But Rosas cracks him up top and surges. Barcelos keeps working though, and he's starting to pull away from Rosas, who has a bit more heart than technique right now.

MMA Fighting scores the round 10-9 Barcelos, 19-19 overall.

Rosas looks a bit refreshed to start the round, but he's not throwing nearly as much as he was. And Barcelos is steady with the right hand. Rosas goes for a single leg but Barcelos stuffs him and then trips him, ending up on top.

Oh this is bad news for Rosas. 90 seconds into the round and Barcelos is on the back with the body lock. But Rosas is doing a good job of working his way around the legs, and he turns! Rosas in the guard now and this is by far his best position.

Rosas postures and starts punching, moving to top half. More punches but Barcelos scoots to the fence and gets up. Now Barcelos grabs a single and pushes Rosas to the fence. Rosas lands a right but Barcelos answers right back. And Barcelos is starting to let the jab fly. He's scoring much more consistently on the feet. Rosas is still willing, though. Both men are bleeding freely. Barcelos grabs a snatch single and pushes Rosas to the fence then lands a huge elbow on the break.

Barcelos' left eye is extremely swollen, and I'm not sure how much he can see out of that right now. But he keeps slipping Rosas' jab and then right to a leg and hits a foot sweep. Barcelos moves to the back very quickly and small punches as Rosas turtles. Rosas gramby rolls to his feet and Barcelos lands a head kick. I honestly have no idea who to score that round for.

MMA Fighting scores the round 10-9 Rosas, 29-28 Rosas.

Rosas' cut on the bridge of his nose is disgusting. Just a huge chunk of flesh is gone. But Barcelos somehow looks even worse, with the left side of his face all mashed up.

Barcelos backing Rosas up with his jab and Rosas hasn't thrown much through the first minute. Barcelos keeps slipping in shots to the body, too. That's paying dividends. And Rosas is in full retreat mode as Barcelos keeps chipping away.

Oh, Rosas is real tired. Barcelos just hit a nice step in to a snatch single and foot sweep, but Rosas dudn't even move to defend. He's slowing seriously. But he turns to turtle and gets to his feet. Barcelos holding him along the fence though and then trips him down again. And as Rosas tries to stand, Barcelos hits an old-man throw down, pulling him back to the ground. Rosas keeps trying to scramble, but Barcelos moving through with it and starting to land some good ground and pound.

And now Barcelos is on the back and working a choke! He's under the neck, but he's off on an angle, and I don't think he can finish this. But Barcelos keeps trying. He looks far off from it and Rosas seems to think he's safe. He's on a good angle and Barcelos bails on it, moving with him and punching.

Oh now this one is better! Barcelos got full backpack and pulled Rosas down, and he's on the jaw, with a palm-to-palm grip! Rosas fighting the hands and doing a good job. He's out of immediate danger, but Barcelos still holding position and with an arm across. Rosas not gonna give up the choke though, and Barcelos punches until the end of the round.

MMA Fighting scores the round 10-9 Barcelos, 38-38 overall.

Per the unified rules, I think you could make an argument for a 10-8 there but most would not. Per my scoring criteria, that is undeniably a 10-8 round for Barcelos. Alas, I don't rule MMA.

Rosas looks rejuvenated to start this final round. But Barcelos looks spry, too. Could be all to play for here, though many have it 3-1 Barcelos right now.

Rosas with a lot of movement and forward pressure, but that fails him as Barcelos ducks under and gets a takedown. Rosas active off the bottomg and Barcelos moves to the back. But Rosas with urgency and he gets out.

Rosas emptying the atnk here, and Barcelos meeting the moment. Rosas fighting like first-round Terrance McKinney but Barcelos surviving for now. But Rosas along the fence gets a trip takedown and Barcelos looks like he might be fading.

Rosas advances to top half. AND BARCELOS IS OUT!!!!!!! I HAVE NO IDEA WHAT HAPPENED, BUT BARCELOS IS COMPLETELY OUT AND NOT MOVING AND ROSAS STEPS OFF HIM.

On replay, it's still unclear what happened. On the takedown, it seems like Rosas got KOed, but it's not an obvious thing that did it. It seems like Barcelos must have his his head coming down, because he was for sure out. Rosas landed one punch and then saw he was out and stepped off.

Crazy ending and finish for Raul Rosas Jr.

Oh wow. Barcelos is still down minutes after the action. The show is not showing him and they are talking in very bad terms. He got put on the stretcher and wheeled out. That is genuinely concerning.

Raul Rosas Jr. def. Raoni Barcelos via KO (slam) — 1:38, Round 5

Very classy from Rosas, who starts by shouting out Barcelos. Hope he's OK.

Rosas then does a “Chiwiwis†and calls for a bonus and a shot at the Top 7.