UFC 155 fight card preview

The Ultimate Fighting Championship rounds out a tumultuous 2012 calendar with an action-packed fight card this Saturday at the MGM Grand Garden Arena in Las Vegas.

Headlining UFC 155, heavyweight juggernaut Junior dos Santos sets out to prove his victory over Cain Velasquez last November was no fluke as they collide in a colossal rematch for the heavyweight championship. Despite a rash of injuries and late changes, a number of compelling matchups will round out the UFC 155 lineup.

Here's a closer look at the UFC's year-end extravaganza:

UFC heavyweight title: Junior dos Santos (15-1) vs. Cain Velasquez (10-1)

Over one year since dethroning Velasquez to lay claim to the UFC heavyweight throne on the promotion's first-ever card broadcast on FOX, dos Santos seeks to further cement his dominance over the division.

Both fighters were battling knee injuries in their first go-around, so we'll see if there are any changes on Saturday night with both men seemingly entering the Octagon at 100 percent.

In nine flawless appearances under the UFC banner, dos Santos, 28, has been nothing short of superb. Stoppages of Fabricio Werdum, Stefan Struve, Mirko "Cro Cop" Filipovic, Gilbert Yvel and Gabriel Gonzaga put the entire division on notice. Subsequent one-sided decisions over Roy Nelson and Shane Carwin established dos Santos as an elite heavyweight. Against Velasquez, however, dos Santos may have made the most emphatic statement of his career, laying out the previously unbeaten champion with a fistic flurry in just 64 seconds.

Most recently, the heavy-handed Brazilian finished Frank Mir in the second round of their title bout in May.

A black belt in Brazilian jiu-jitsu, the Team Nogueira prodigy has yet to showcase his grappling pedigree. The reason being, of course, that he hasn't had a reason for it. Instead, the Luiz Dorea-trained boxer elects to keep fights standing, picking his shots at will and breaking his opponents down, both mentally and physically.

Despite one professional setback via submission against Joaquim Ferreira in November 2007, dos Santos could very well be the sport's most dangerous specimen.

In addition to possessing sublime submission prowess and boxing smarts, dos Santos has one of the best sprawls in the UFC, having spent less time on his back than any other fighter on the roster with the exception of middleweight wrestler Chris Weidman.

Although mixed martial arts is a multi-faceted game, dos Santos has done just fine relying solely on his hands and takedown defense. He holds the record for most knockdowns in UFC heavyweight history, as nine opponents have fallen when his heavy hands find their target.

Velasquez, 30, is coming off one of his most impressive performances to date, as he battered and bloodied Antonio Silva en route to a first-round stoppage at UFC 146.

Before losing his belt, Velasquez was undefeated with notable wins over Brock Lesnar, Antonio Rodrigo Nogueira, Ben Rothwell and Cheick Kongo.

A former two-time NCAA Division I All-American and Pac-10 Conference wrestling champion, Velasquez has honed his skills at San Jose's American Kickboxing Academy.

Under the tutelage of Javier Mendez and Bob Cook, Velasquez has benefited from training alongside the likes of Daniel Cormier, Muhammed Lawal and Jon Fitch.

Despite a vast wrestling base, Velasquez has adapted tremendously well to the striking game, landing 17.2 strikes per minute, a UFC record in any division, which is an especially impressive feat for a heavyweight.

Velasquez is highly well-rounded, but he needs to test dos Santos in the clinch and on the ground to emerge triumphant. He successfully landed low kicks early in his first meeting with dos Santos before falling victim to a combination.

This time around, Velasquez needs to spend less time exchanging with the champion and more time feverishly pushing for takedowns. With a smoldering 66.7 percent takedown accuracy rate, Velasquez has a clear advantage he must exploit. We have yet to see dos Santos in a precarious position on the ground, which is where Velasquez has done some of his best work.

Velasquez should find more success in the rematch, and he would certainly benefit from forcing the fight into deep waters. We know Velasquez is a cardio machine, while dos Santos has rarely gone the distance. We also saw signs of dos Santos' fading gas tank in his fight with Nelson at UFC 117.

However, dos Santos' immaculate sprawl and counterpunching should be the deciding factors on fight night. The taller Brazilian will scramble out of bad positions and make the challenger pay with his power punches.

Arguably the best boxer in the UFC, dos Santos will inevitably find a home for a sharp uppercut or brutal overhand right before he capitalizes on the opportunity to unleash an onslaught of fight-ending blows, putting to rest any illusions about a fluke when he won the championship.

Verdict: dos Santos via TKO, Round 4

Joe Lauzon (22-7) vs. Jim Miller (21-4)

In an exciting lightweight bout, the 11-time bonus winner Lauzon tangles with the four-time bonus recipient Miller.

Lauzon, 28, a Brazilian jiu-jitsu purple belt, has the second most post-fight bonuses in promotional history, second only to pound-for-pound king Anderson Silva.

The Massachusetts native is coming off a third-round submission of Jamie Varner this past August, which earned him a total of $100,000 for both Fight of the Night and Submission of the Night honors.

Lauzon made his presence felt in his UFC debut in September 2006, scoring a shocking first-round knockout over then-top contender Jens Pulver, still regarded as one of the biggest upsets in history.

Despite hiccups throughout his UFC journey, dropping fights to Kenny Florian, Sam Stout, George Sotiropoulos and Anthony Pettis, Lauzon has notched some impressive submissions over Jeremy Stephens, Gabe Ruediger, Curt Warburton and Melvin Guillard.

Miller, 29, a black belt in Brazilian jiu-jitsu under Jamie Cruz, was finished for the first time in his career in his most recent outing, succumbing to a second-round guillotine choke against recent title challenger Nate Diaz.

It was his second setback in three appearances, as he suffered a decision loss to current champion Benson Henderson in August 2011.

However, the New Jersey native was previously riding a seven-fight winning streak. His UFC victims include a slew of top contenders, such as Guillard, Charles Oliveira, Gleison Tibau, Mark Bocek, Mac Danzig and Matt Wiman.

In addition to his submission skillset, Miller comes from a collegiate wrestling background, and he often bullies opponents on the ground.

Both competitors come from fighting families with brothers who have competed in the UFC. Lauzon has often served as a mentor to his younger brother Dan Lauzon, who was 0-2 in the UFC, while Miller got his start by learning from his older brother Dan Miller, who has amassed a 6-5 UFC record.

Miller will be successful if he catches Lauzon off balance and plants him on his back. Miller should also get the best of critical striking exchanges. Lauzon is a slick submission stylist, and he will likely have his moments, but Miller should have his number there as well. Most importantly, Lauzon has often struggled from gassing out early in his bouts.

If Miller can employ his style of grueling close combat, Lauzon will begin to fade midway through the fray. Miller's unrelenting pressure and sizeable strength advantage will be the difference makers as he comes away with the decision.

Verdict: Miller via decision

Tim Boetsch (16-4) vs. Constantinos Philippou (11-2)

In a compelling middleweight meeting, the red-hot contender Boetsch battles unheralded short notice replacement Philippou.

Boetsch, 31, has reinvented himself since making the cut to 185 pounds following losses to the likes of Vladimir Matyushenko, Matt Hamill, Jason Brilz and Phil Davis at light heavyweight.

Boetsch is a former NCAA Division I wrestler, but the Jeet Kune Do black belt possesses heavy hands and a granite chin, which have helped establish the Maine native as a bona fide contender.

Since dropping to middleweight, Boetsch is undefeated with wins over Kendall Grove, Nick Ring, Yushin Okami and Hector Lombard.

Philippou, 33, a native of Cyprus, has come a long way since arriving in the U.S. as a one-dimensional boxer. Philippou has earned his Brazilian jiu-jitsu blue belt training under Matt Serra and Ricardo Almeida in New Jersey, while further expanding his striking with Ray Longo.

After falling short in his bid to become a cast member on the 11th season of "The Ultimate Fighter," Philippou joined the UFC in March 2011, dropping a decision to Nick Catone. Philippou has since built an impressive four-fight winning streak over Jorge Rivera, Jared Hamman, eventual "TUF 11" winner Court McGee and Riki Fukuda.

The hard-hitting southpaw has showcased great takedown defense and a competent striking game as he's progressed in his career.

Boetsch, who was initially expected to face surging prospect Chris Weidman before an injury forced the bout's cancellation, is by far Philippou's toughest test to date. He will need to test Philippou in all positions, where he should get the better of key exchanges. Philippou's durability has never been doubted, but Boetsch's superior wrestling and positional control will earn him a hard-fought judges' decision.

Verdict: Boetsch via decision

Alan Belcher (18-6) vs. Yushin Okami (27-7)

In a rematch of the first bout in their respective UFC careers, Belcher and Okami will get it on again.

The 28-year-old Arkansas native Belcher has been on a roll as of late, dispatching Wilson Gouveia, Patrick Cote, Jason MacDonald and Rousimar Palhares on his way to a four-fight winning streak.

Belcher had previously knocked off Jorge Santiago, Ed Herman and Denis Kang, with many pundits also believing he deserved the nod against Yoshihiro Akiyama in a split decision that went the other way at UFC 100.

A Brazilian jiu-jitsu black belt, judo brown belt and Duke Roufus-trained kickboxing black belt, Belcher has evolved into one of the division's most dynamic contenders.

Belcher's career is obviously on the rise, while Okami finds himself at a crossroads.

Okami, the 31-year-old Japanese warrior, has imposed his dominant wrestling game to earn UFC wins over Belcher, MacDonald, Evan Tanner, Dean Lister, Mark Munoz and Nate Marquardt.

Okami has fallen short twice in title bids against Rich Franklin and Anderson Silva and a shocking TKO loss to Tim Boetsch last February has dropped him down the list of contenders. Okami was victorious against Buddy Roberts at UFC 150 this past August, but it marked a significant step down in competition.

Still, the judo black belt is one of the worst matchups for any middleweight in the UFC, as he employs a grinding style and punishes foes with underrated boxing.

Okami was dominating Boetsch until he was finished in the third round, so time will tell if the left-hander has really lost a beat.

Okami is most effective when he initiates clinches and punishes adversaries in close quarters. Meanwhile, Belcher should have an edge if he can keep the fight upright and use his movement to stifle Okami's potent jab. It will likely be competitive from start to finish, but Belcher could earn the razor-thin nod this time around if he remains aggressive throughout and lands crisper combinations.

Verdict: Belcher via decision

Derek Brunson (9-2) vs. Chris Leben (22-8)

Making his UFC debut on short notice, the Strikeforce veteran Brunson could make a name for himself with a victory over a household middleweight name like Leben.

Brunson, 28, a three-time NCAA Division II All-American, has split time training at Renzo Gracie Jiu-Jitsu and Jackson's MMA.

Brunson suffered his first loss in a highly controversial decision against Kendall Grove this past June before his first knockout loss against Ronaldo "Jacare" Souza in August.

Despite a two-fight losing streak, Brunson is a quality prospect with strong takedowns and top control.

Leben, 32, is competing for the first time in over a year after suffering a second-round TKO loss against Mark Munoz at UFC 138. Post-fight, Leben tested positive for banned painkiller oxycontin.

It was an unfortunate turn of events for the "TUF" season 1 semifinalist, who was coming off a career-defining moment as the heavy-handed southpaw knocked out Wanderlei Silva in just 27 seconds at UFC 132.

Leben's UFC career has had its ups and downs. Between run-ins with the law and failed drug tests, Leben has been one of the most inconsistent fighters on the roster. He's dropped fights to Anderson Silva, Jason MacDonald, Kalib Starnes, Michael Bisping, Jake Rosholt and Brian Stann, while finishing the likes of Yoshihiro Akiyama, Aaron Simpson, Alessio Sakara, Terry Martin, Jorge Santiago and Jorge Rivera.

A longtime Team Quest representative and current Icon Fitness MMA product, Leben is actually well-schooled in all areas of the game. A tough chin, heavy hands, crafty submissions and a strong wrestling base should not be overlooked when assessing the tools Leben brings to the table.

After Leben's prolonged layoff, we'll need to see how he  reacts to Brunson's constant takedown attempts. Leben is undoubtedly the more dangerous striker, and he should be favored to punish Brunson standing, but nothing is ever certain with "The Crippler."

Brunson will likely have a hard time taking Leben down, let alone keeping him there. Leben has never shied away from a brawl, and Brunson has not yet had to react to wild storms of punches. Leben will change that on Saturday night as he blitzes Brunson in the first round to mark a successful Octagon return.

Verdict: Leben via KO, Round 1