A lot of hats in attendance tonight, are you a fan or nah?

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We're into the fourth round in the co-main event and it's certainly not being fought at the speed of the previous fight but still an intriguing one.

It's fairly even but Walsh has landed more to the head and body despite Vargas' high guard.

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Terence Crawford is boxing's humble king.

"I never set my sights out to be the face of boxing. It was never my goal," Crawford told BBC Sport.

"I just want to win. [Canelo] can be the face of boxing. Just give me everything in the background that comes with it."

Some remarkable names on each man's record. Who do you think has the better resume?

Saul 'Canelo' Alvarez:

• Jermell Charlo (W)
• Dmitry Bivol (L)

• Billy Joe Saunders (W)
• Callum Smith (W)
• Sergey Kovalev (W)
• Gennady Golovkin (D,W)
• Amir Khan (W)
• Floyd Mayweather (L)
• Shane Mosley (W)

Terence Crawford:

• Israil Madrimov (W)
• Errol Spence Jr (W)
• Shawn Porter (W)
• Kell Brook (W)
• Amir Khan (W)
• Ricky Burns (W)

Anthony Crolla
Former world champion to BBC Sport

People are asking if size will be a big factor. I was lucky enough to see Canelo up close when I was in the corner for my mate Callum Smith - he had a very thick set. But I do believe Crawford has taken his time building up to the weight, he's unbelievably strong. People forget what a good wrestler away from boxing he is.

His biggest strength is that he's so versatile. He can go orthodox or southpaw, fight on the inside or outside, he can do it all. I think timing could be perfect here. It may be a chess match - no thrills and spills - but I think Crawford edges it on points. He may have to take one or two big 'uns and weather the storm, though.

Kal Sajad
BBC Sport at Allegiant Stadium, Las Vegas

Is Saul 'Canelo' Alvarez on the decline?

His last outing against William Scull was flat. Scull didn’t come to fight, but Alvarez couldn’t find a way to shine either, growing frustrated chasing a man who never engaged.

Yes, Alvarez is younger than Crawford. But remember, he turned pro at 15. Nearly 20 years as a pro takes its toll. If he loses tonight, it’ll sting more than the Dmitry Bivol defeat, because this time he’d be losing to the smaller man.

He’s a legend already, but whispers of retirement won’t be far behind if Terence Crawford dethrones him.

Saul 'Canelo' Alvarez didn't take too kindly to suggestions boxing is declining.

Have a watch of what the Mexican had to say.

Terence Crawford may be going for history, but let's not forget there is one person who has already achieved being a three-weight undisputed champion in the four-belt era.

And that is, of course, Claressa Shields. The American has been undisputed at light-middleweight, middleweight and heavyweight.

Crawford certainly hasn't forgot her this week, mentioning her on several occassions. Boxing bromance.

"She’s done wonderful things in the sport of boxing," he told BBC Sport.

"She’s a tremendous talent. That’s a good friend of mine and for me to become the first male three-weight undisputed champion and sit alongside her is something to see."

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Dana White is planning big changes to boxing, providing he can get those changes to the Muhammad Ali Act done.

That is still going through American halls of power and there has been a lot of pushback to Athletic Commissions in the United States who are backing the bill.

BBC Sport caught up with White on Friday.

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Callum Walsh was working on a fishing boat seven days a week during Covid-19. It was gruelling work and when the boxing stopped, Walsh decided he would move to LA, knock on the door of Roach’s Wild Card Boxing Club gym door and ask to train there.

“I was making no money. Sleeping on the couch for a long time. I bought a car and then I crashed it. So many things happened that I thought I should go home,” Walsh said, but he stayed, got his green card and would return to Ireland a 3-0 professional boxer.

He credits the fishing job, along with his own relentless personal drive, with keeping him focussed.

“It showed me that I don’t want to go back there. It was tough, it showed me hard work. I think it made me the man I am today.

“Made me work hard in the gym. Made me see the reality of life. I am living in dreamland now in comparison.”

Ireland's Callum Walsh takes on Fernando Vargas in the top undercard fight in Las Vegas.

But who is Walsh? For those of you who don't know he happens to be Dana White's favourite boxer.

He has fought the majority of his boxing career on UFC Fight Pass, with White in his corner, and was handpicked by White for the co-main event for Canelo Alvarez v Terenece Crawford.

“Doesn’t make sense because I’m a boxer. It just doesn’t make sense,” Walsh told BBC Sport.

“Dana seen the mindset I had, the skills I had and I think the perfect one to represent the boxing side of the UFC.”

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Up next is the co-main event with Ireland's Callum Walsh taking on Fernando Vargas.

We won't be doing round-by-round updates for this one but you'll get updates along the way.

We've just seen a wonderful fight between Lester Martinez and Christian Mbilli end in a draw.

It was a 12-round war at super-middleweight and we were exhuasted just watching it.

Both men landed big shots and never let up. Pure guts, all action.

Image source, Getty Images

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Kal Sajad
BBC Sport at Allegiant Stadium, Las Vegas

There’s still one more bout before the main event, but Allegiant Stadium is already heaving.

The undercard may have lacked star power, yet nobody is budging from their seat.

When Alvarez appeared on the big screen having his hands wrapped, the place erupted as if the darling of Guadalajara was making his ring walk.

Image source, Getty Images

Kal Sajad
BBC Sport at Allegiant Stadium, Las Vegas

One of the big storylines this week has been UFC boss Dana White crossing into boxing with his first Zuffa Boxing promotion. And it’s not without controversy.

Right now, the Muhammad Ali Act - passed in 2000 - protects fighters from promoters having too much control. It forces promoters to disclose financial details to boxers, bans conflicts of interest (so the promoter can’t also act as manager), and makes sure the fighter, not the promoter, is the one who ultimately decides their own career path.

White says boxing is “broken.” He told BBC Sport that his vision does not include the sanctioning bodies - WBC, WBA, IBF, WBO - with all their belts and fees, and wants a streamlined UFC-style model: one organisation, one set of titles, exclusive contracts for fighters.

His critics say that’s exactly the problem. Under the UFC system, fighters earn a far smaller share of event revenue compared with boxers, have little say over opponents or purses, and can be tied to restrictive deals.

The Ali Act doesn’t apply to MMA, and that's why White is lobbying to have it changed.

When pressed on it this week in Vegas, he shut down the questions. But if tonight’s Netflix blockbuster proves his model can deliver eyeballs and money, boxing could be heading for a huge shake-up.