UFC 155: Four burning questions going into ‘Dos Santos vs. Velasquez 2' in Las Vegas

This Saturday night (Dec. 29, 2012), the Octagon returns to "Sin City" for its final event of the year as UFC 155: "Dos Santos vs. Velasquez 2" goes down at the MGM Grand Garden Arena in Las Vegas, Nevada.

A heavyweight championship contest receives top billing as Junior dos Santos takes on Cain Velasquez for the second time in the main event of the evening. There are several interesting storylines to follow going into and coming out of the event, but only four can make the "burning" list.

That being said, here are four burning questions going into UFC 155: "Dos Santos vs. Velasquez 2" this weekend:

4. Can Chris Leben make good on his third chance?

Thirteen months after being suspended for a failed drug test following his UFC 138 defeat to Mark Munoz in Nov. 2011, one of the most popular fighters in Ultimate Fighting Championship (UFC) history, Leben, returns to mixed martial arts (MMA) competition on the main card of UFC 155 when he takes on the debuting Derek Brunson.

On the heels of his second drug suspension in three years -- the first was a positive test for Stanozolol following Leben's unanimous decision defeat to Michael Bisping at UFC 89 -- "The Crippler" could be on his last legs with the organization and cannot afford another mistake, even though UFC President Dana White has publicly supported the middleweight fighter though his personal problems.

Since his stint on the debut season of The Ultimate Fighter (TUF) reality show in 2005, Leben has been one of the organization's most consistently exciting fighters over the course of his 19 appearances inside the Octagon.

But, more important than Leben's fighting career is his mental health, and after a forced leave of absence from the sport because of suspension, it appears the 32-year-old has used the time away to give himself a fresh start.

Last March, Leben talked at length about his battle with alcohol and substance addiction, but now he seems to be in a good place mentally, and from the looks of it he is in great physical shape, too.

The Oregon native may never be a top contender or world champion, but when he's got his head on straight (or as straight as a professional fighter can be), Leben is a pleasure to watch and his fights are always a candidate for a post-fight bonus.

3. Is the winner of Brad Pickett vs. Eddie Wineland the No. 1 contender at 135-pounds?

An opportunity to be the No. 1 contender in the UFC bantamweight division could be on the line when two of the world's hardest hitting 135-pounders do battle on the "Prelims" portion of the UFC 155 fight card when British fan-favorite Brad Pickett returns to the Octagon against grizzled veteran Eddie Wineland in a fight that should be loaded with action.

Pickett is riding high on the heels of a first-round knockout of Yves Jabouin this past September at UFC on FUEL TV 5. The British fighter is 2-1 in his three appearances under the UFC banner and has won post-fight bonuses in both of his victories. The 34-year-old has fought all of his UFC bouts overseas and will travel stateside to fight for the first time since joining the organization.

Wineland started his UFC career with an underwhelming record (0-2), but scored his first Octagon victory in dramatic fashion at UFC on FX 3 when he knocked out Scott Jorgensen in the second round. The 28-year-old is one of the most powerful strikers in the world at 135-pounds as 10 of his 19 wins come by (technical) knockout, including knockout finishes in his last three wins.

With UFC bantamweight champion Dominick Cruz on the shelf until late 2013 because of a second knee surgery and interim title-holder Renan Barao set to defend against Michael McDonald at UFC on FUEL TV 7 next February, it's likely the Barao-McDonald winner will have to fight again before unifying the titles with Cruz. If that's the case, look for the winner of Pickett vs. Wineland to get the shot if they earn an impressive victory.

2. Will Alan Belcher avenge his loss to Yushin Okami? Or will "Thunder" repeat history?

When Belcher and Okami meet in one of the featured bouts at UFC 155, it will be a rematch of their 2006 encounter at UFC 62, which saw Okami walk away the winner by unanimous decision. More than six years later, Belcher and Okami are set to do battle for the second time.

Belcher has evolved tremendously since his first run-in with Okami, but has been hampered by injuries in recent years, which up until his last fight -- a first round technical knockout of Rousimar Palhares at UFC on FOX 3 -- prevented him from building any real ground in the UFC middleweight division.

"The Talent" has only competed three times since the beginning of 2010, but is now completely healthy and is looking to make a title run at 185-pounds. The 28-year-old has won six of his last seven bouts with the lone loss coming via controversial split decision against Yoshihiro Akiyama all the way at UFC 100 in July 2009.

Okami got back in win column last August at UFC 150 when he defeated an overmatched Buddy Roberts by second-round technical knockout. After losing back-to-back fights to Anderson Silva and Tim Boetsch, the Japanese fighter rebounded with a dominant performance and reasserted himself back "into the mix," as UFC President Dana White would say.

Okami is a dominant wrestler with respectable boxing skills who holds a 10-4 record under the UFC banner with four of his last six fights ending by (technical) knockout. Belcher is the favorite going into the rematch, and if Okami can defeat the Duke Roufus-trained fighter he will prove he is still worthy of being included in conversation when people discuss the world's best 185-pouner fighters.

Will Okami be able to repeat history and hand Belcher another loss? Or is "The Talent" going to avenge his loss to Okami over six years later?

1. Will the ground game of Junior dos Santos finally be tested?

Junior dos Santos has competed nine times inside the UFC's Octagon -- his skills on the ground still remain a mystery.

Every time "Cigano" has stepped in the cage against the world's best heavyweights, he has shown the ability to keep his fights on the feet and obliterate his opposition with a devastating striking arsenal.

The Brazilian has avoided takedown attempts from skilled wrestlers such as Cain Velasquez, Roy Nelson and Shane Carwin, and has also knocked out world-class grapplers like Fabricio Werdum and Frank Mir before they even had the chance to execute on the ground.

At UFC 155 this Saturday night, dos Santos will meet Velasquez for the second time. Velasquez is by far the most accomplished wrestler to have ever challenged the champion, and even though he was knocked out in his 64-seconds in the first meeting with dos Santos at UFC on FOX 1 in Nov. 2011, he is still the division's best hope at testing dos Santos' ground game.

Velasquez has shown time and time again the ability to take opponents down at will and land some trademark ground-and-pound, the most brutal of which may have been in his last fight against Antonio Silva last May. Dos Santos must do everything in his power to stop that from happening.

Unless the rematch is a mirror image of the first bout and dos Santos take out Velasquez quickly, Saturday night could be the first time dos Santos is truly forced to fight off his back.

The ability to stop takedowns is one thing, having a relentless animal like Velasquez in dominant top position it entirely different. How dos Santos reacts if put on his back could be the deciding factor in who comes out of UFC 155 as the UFC heavyweight champion of the world.