As UFC 137 quickly approaches, fans across the globe patiently wait for the drama-filled fight card that will take place on Saturday, Oct. 29th.
With Georges St-Pierre out with a knee injury, the main card will be headlined by former UFC champion BJ Penn, who will square off with dangerous Nick Diaz.
While UFC 137's fighters have made it to the highest stage in mixed martial arts, there was that one career-defining moment that changed their careers forever.
The following slides display the career-defining moment for each fighter on the main card at UFC 137.
Lets take a look.
While Hatsu Hioki entered the sport of mixed martial arts in October of 2002, it wasn't until years later when his career was changed for the better.
In May of 2006, Hioki squared off with Mark Hominick in a non-UFC bout at TKO 25.
At the time, Hominick was the TKO Major League Featherweight champion when he stepped foot inside the Octagon with Hioki.
Hominick was dethroned by Hioki as he was submitted via Triangle Choke in what would end up being Hioki's career-defining moment.
George Roop makes his second return to the UFC after being cut following his loss to George Sotiropoulos at UFC 101.
Roop continued his career in mixed martial arts, which eventually led to a bout with Leonard Garcia at WEC 47.
While the fight ended in a draw, it was one of the most exciting fights of Roop's career as it earned Fight of the Night. More importantly, it provided motivation for his path back to the UFC.
Scott Jorgensen entered WEC 50 to take on Brad Pickett, which was considered the biggest fight of his career at the time.
Pickett was on a nine-fight win streak after defeating Demetrious Johnson at WEC 48. The only thing standing in the way of a title shot for Pickett was Jorgensen himself.
In what would go down as the Fight of the Night, it was Jorgensen who outlasted Pickett via unanimous decision.
Jorgensen's win earned him a title shot against Dominick Cruz at WEC 53.
In just the second WEC fight of his career, Jeff Curran entered the Octagon in Las Vegas, Nev. to take on Stephen Ledbette in a Featherweight bout.
At the time, Curran was on a five-fight winning streak and showed no signs of slowing down as he dominated action early.
Curran went on to defeat Ledbette, earning a title shot against Urijah Faber at WEC 31.
It's hard to label a career defining moment for Mirko "Cro Cop" Filipovic as it seems he's been around the sport of mixed martial arts since it first began.
It was Sept. 2006 when Cro Cop earned his way to the Pride Grand Prix Finals where he met Josh Barnett.
Cro Cop displayed one of the greatest performances of his career as he began pounding away on Barnett.
With 7:32 remaining in the first round, Cro Cop was declared victorious and named the 2006 Pride Grand Prix champion.
Roy Nelson entered the Ultimate Fighter: Heavyweights Finale in 2009 as one of the most experienced fighters on the show.
Nelson was set to square off with heavy hitter Brendan Schaub in the championship in front of a sold out Las Vegas crowd.
It was Nelson who reigned supreme after knocking out Schaub at 3:45 of the very first round, taking home the Ultimate Fighter championship and Knockout of the Night honors.
While Cheick Kongo has fought in 14 different UFC events, his career-defining moment didn't come until recently, when he met Pat Barry at UFC Live in June of 2011.
In what would go down as one of the best fights of the entire year, Barry had Kongo down to the ground as he began to pound away.
Kongo recovered to his feet only to be knocked down once more.
Then, out of nowhere, Kongo connected on a strike that knocked Barry out cold, capturing arguably the biggest win of his mixed martial arts career.
While Matt Mitrione may be one of the most inexperienced fighters heading into UFC 137, he's also one of the most dangerous.
Posting a perfect 5-0 record in UFC contests, Mitrione's career defining moment came when he met heavy hitter Joey Beltran at UFC 119.
In the most exciting fight of the evening, Mitrione outlasted Beltran, letting the rest of the world know he was, in fact, a legitimate Heavyweight contender.
While there are many events or instances that could define Nick Diaz's career, we'll stick with the positive.
It was Feb. 2007 when Diaz entered arguably the biggest fight of his mixed martial arts career against Takanori Gomi at Pride 33.
Diaz was dropped by Gomi as his night appeared to be coming to an end. Diaz then shocked the world by bouncing back and connecting on one of the greatest submissions in MMA history.
Unfortunately for Diaz, his victory over Gomi no longer stands as the bout was ruled a no contest following a failed drug test by Diaz.
BJ Penn is undoubtedly one of the greatest mixed martial artists to have ever set foot inside the UFC Octagon.
While Penn has many historical career defining moments, it was nearly a year ago when the "Prodigy" took on fierce rival Matt Hughes in one of the most anticipated bouts in UFC history.
In Penn's return to the Welterweight division, he attacked Hughes right out of the gate, ending his night in a jaw-dropping 21 seconds.
Not only did Penn avenge his loss to Hughes at UFC 63 for the Welterweight championship, but he proved to the world why he is in fact one of the greatest fighters of all time.