This Sunday when former WEC World Bantamweight Champion Urijah Faber steps into the cage in front of his hometown Sacramento crowd, he'll be venturing back into mostly unfamiliar territory.

For the first time in more than four years, he'll be standing across the cage from the champion, and for the first time ever in his fighting career he'll be the former champion trying to re-stake his claim as the best 145 pounds has to offer.

But while Faber has established himself in recent years as one of the premier MMA fighters in the lower weights, playing the role of spoiler won't be completely foreign to him; in fact, it's all he did when he started out in the sport.

In just his third fight, he dispatched UFC veteran David Velasquez.

He won the WEC title in 2006 with a TKO victory over Cole Escovedo, who at the time was considered by many to be the top bantamweight fighter on the West Coast.

Faber's next fight was a submission victory over Charlie Valencia, who had been the dominant fighter under 155 pounds in the King of the Cage ranks.

By the time WEC was bought by UFC parent company Zuffa and launched its presence on cable television, Faber had positioned himself to be the star of the company.

But he still had to prove his worth by beating two challengers with steeper pedigrees and longer MMA resumes in Jens Pulver and Jeff Curran, which he did in dominant fashion, silencing many critics along the way.

As the reigning WEC champ, Faber had only tasted defeat one time: a September 2005 TKO loss to current UFC 155-pound star Tyson Griffin, who used a dominant strength advantage to muscle Faber around the cage before a nasty staple-requiring cut to Faber's head signaled the end.

Unfortunately for Faber, that loss appears to have been the start of a trend that exposes a weakness in his game for which there may be no easy fix.

As we saw in his most recent defeat at the hands of Mike Brown, being at a size and strength disadvantage doesn't bode well for "The California Kid."

Speed, endurance, unpredictability, and tenacious overall style aside, Faber's lack of size and power in comparison to Brown makes him an underdog in this fight, much as he should have been the first time around.

While it certainly doesn't guarantee a loss (Faber built his career handling guys that were supposed to beat him), it cancels out the popularity advantage he carries over the current champ that no doubt will have many casual fans expecting Faber to win.

Consider the common theme of the fights on Faber's resume: when size and strength are equal, he wins. When he carries the size and strength advantage, he dominates.

The only times his opponents have had size and strength on their side, have been his only two losses.

Now consider that Faber, no matter how much people might like to compare him to 155-pound fighters, is more built for 135, and the fact that he has spent his career carving up the 145-pound class makes him all the more impressive. At the same time, it doesn't bode well for his chances against a beast like Brown.

As a 155-pound fighter, Brown had reasonable success, even notching a win over former top-ten fighter Yves Edwards. Since dropping to 145, he has been nothing short of destructive. In fact, no one has been able to match his power or fight through it.

Brown is said to routinely spar with 170-pound American Top Team teammates, a list that includes Luigi Fiorivanti and wrecking machine Thiago Alves.

In fact, ATT fighters are notorious weight cutters, weighing in 10-20 pounds heavy at fight time.

Add that fact to Faber's admission last week on Bay Area sportstalk station KNBR that he has a hard time keeping his weight up, and its clear that the former champion has a steep hill to climb Sunday night.

Fortunately for Faber, he is in a great position regardless of the outcome in this fight. The fact is, superfights await him regardless, at multiple weights.

Win and he sets up the greatest trilogy in the greatest rivalry to date in WEC, a third bou with Brown. Another victory there and he could toy with the idea of moving up and challenging the UFC's 155 pound champion, though his chances there are very slim.

A loss, however, opens new doors for Faber.

With 145 pounds firmly in Brown's control, he can create an new beginning, a new identity, as a featherweight, challenging what could be the best overall pound-for-pound fighter in the world.

Miguel Torres still has undefeated Brian Bowles on his slate, but it wouldn't be far-fetched to expect him to retain his title in that bout.

With Faber being naturally built for the 135 division, he could create an incredible matchup stylistically with Torres, and the fireworks in that fight would be about as certain as it gets in MMA.

The best part is a move to 135 by Faber wouldn't be out of necessity; with him having already dominated 145, WEC could promote it as the former champion seeking out new challenges. The amount of exciting new matchups it would create could fill WEC main events for quite a long time.

When you assess Faber's overall success in MMA, you have credit him for doing what once seemed impossible by making himself one of the most well known fighters in the world despite being too small for the UFC.

In essence, Faber is the closest thing MMA has to Oscar De La Hoya.

No, he's not going to generate multi-million-dollar pay-per views and become one of the most lucrative brands in all of sports; but what he is is the most relevant fighter in the world under 170 pounds, one who has headlined more cards than BJ Penn and is seen on weekly cable television more than Georges St. Pierre.

Faber has taken his in-cage success and translated it into real life success, generating lucrative sponsorships, opening his own gym, and becoming one of the most marketable fighters out there.

It's because of that combination of outstanding physical talent and keen business sense that Faber's future only gets brighter following his fight with Brown.

And either way, his fans are in store for great battles for some time to come.