The UFC’s 20th anniversary is quickly approaching. This has been a time for fans to reminisce. A time for fans to remember the beginning of our sport, to recall how close the sport came to dying under political pressure, and to celebrate its current height of popularity. It is also a time to remember the stars who captured our imagination and changed the sport forever. A time to remember the great fights and bitter rivals. Who could forget Royce Gracie dominating bigger men or Ken Shamrock attempting to play his foil? Who could forget fighters like Mark Coleman or Frank Shamrock who changed the sport forever? Or the rivalries between the Lion’s Den and Tito Ortiz, or, by contrast, Chuck Liddell and Randy Couture’s respectful battles as the two best fighters in the division, or Brock Lesnar’s intense wars with Frank Mir? Who will forget the stars of each era that we have cheered non-stop, including the likes of Chuck Liddell, George St-Pierre and Anderson Silva?

But on the other side of the coin, what about those fighters who could have achieved that level of success, but never did? There are a lot of reasons fighters haven’t lived up to their potential. For some, it was matter of not being able to stay healthy. For others, it was mental. And for others still, they just didn’t have the desire or focus to get ahead. Regardless of the reason, here are the top 10 fighters in UFC history who never lived up to their potential:

10. Rameau Thierry Sokoudjou

Rameau Thierry Sokoudjou exploded onto the MMA scene. He was a skilled judoka, winning three national titles in Cameroon and capturing the U.S. National Championship before moving to MMA. Sokoudjou fought primarily on the regional circuit when Pride decided it wanted to feed him to one of its top-ranked fighters, Antonio Rogerio Nogueira. Sokoudjou shocked the world when he became the first (and still only) fighter to knock out Nogueira, and then followed that performance up with a knockout of top-five-ranked Ricardo Arona.

The promise Sokoudjou showed early in his career has not been seen since, including during his three-fight UFC stint, where he suffered losses to Lyoto Machida and Luiz Cane. The mixture of heavy hands and his judo credentials made Sokoudjou a dangerous fighter who went 4-1 with two victories over highly ranked opponents early in his career. Since then, however, he has focused on going for the knockout and has become a one-dimensional fighter, going 10-10 and never beating another ranked opponent.

9. Roger Huerta

The Sports Illustrated jinx may not just be for football and baseball players. Roger Huerta was a fast-rising prospect. He started his career by going 20-1-1 (1 NC), including a 6-0 start in the UFC. During this run, Huerta became the first MMA fighter to ever grace the cover of Sports Illustrated and had gained a major push from the UFC.

However, Huerta began to complain about the UFC—about the pay, about the media responsibilities, about per diems given for travel—straining the once solid relationship. Adding to the strain, Huerta began to talk about his desire to model and act, adding questions to whether he would re-sign with the promotion. In response, the UFC threw him in with the top fighters in the division. In the end, Huerta made two little-regarded movies and has gone just 1-6 since he divided his focus.

8. Todd Duffee

Todd Duffee has a bodybuilder’s physique, explosive athleticism, great boxing techniques for the division and knockout power. So, what could go wrong for this “can’t-miss” prospect? Duffee started his career by going 6-0 while spending less than seven minutes in the cage and setting the UFC’s fastest knockout record in the process. In his seventh fight, he completely dominated his opponent, but was caught in the last round. He was cut from the UFC a few months later. While he only had two fights in the UFC, he was scheduled for another three fights that he had to pull out of due to injuries.

After going 1-1 outside of the UFC, Duffee was brought back as a short-notice replacement. He won the fight, but suffered another injury that has kept him out for all of 2013. Duffee can’t stay healthy long enough to establish himself and realize his potential.

7. Lee Murray

Lee Murray’s life would make a hard-to-believe Hollywood movie. He had a less-than-honest childhood involving drug dealing, gangs, violence and arrests. However, Murray found a calling in MMA. He strung together a 7-1-1 record that included a win over the legendary Jose “Pele” Landi-Jons and outside the cage had the now legendary back-alley brawl with Tito Ortiz that led to the UFC offering him a contract. Murray defeated Jorge Rivera in the first round in his only UFC fight and immediately called out UFC poster-boy Ortiz. Unfortunately, Murray had Visa issues that prevented him from competing in the organization again. He only had one more MMA fight in his career. It was against Anderson Silva, and Murray lost a decision.

A few months after fighting Silva, Murray was stabbed in a brawl at a model’s birthday party. The following year, he was arrested for being the mastermind behind the largest cash robbery in British history. Murray is not the first and won’t be the last athlete who can’t leave their past behind, only to discover that it derails their athletic dreams.

6. David Terrell

David Terrell may be the least-known fighter on this list, but his potential to be an all-star was almost unmatched. Terrell was a high school wrestler and one of Cesar Gracie’s first black belts. He won several grappling tournaments, including a bronze medal at the Abu Dhabi Combat Club (ADCC) Submission Wrestling World Championship. In MMA, Terrell lost his first fight, but then won four in a row (all by stoppages, including three ending in the first round).

The UFC decided that it was going to start a middleweight division and created a four-man tournament featuring Matt Lindland, Robbie Lawler, Evan Tanner and the newcomer, Terrell. Lindland was the favorite to win the whole thing and was matched up with Terrell, the least likely to win it all. It took Terrell just 24 seconds to put Lindland to sleep and challenge to be the first UFC middleweight champion. Tanner beat Terrell, but Terrell rebounded by finishing Scott Smith, again in the first round.

Unfortunately, that really was the end to a very promising career. Injuries forced Terrell off of three separate events, eventually prompting the UFC to cut him. Other organizations were ready to sign him, but he could not get healthy enough to compete. As recent as late 2010, Terrell was still talking about making a comeback, but he has been unable to do so.

5. Brandon Vera

There was a time when Brandon Vera announced he would be the first-ever simultaneous light heavyweight and heavyweight champion and no one thought it was out of the realm of possibilities. Vera came into MMA with a strong wrestling background, vicious kickboxing and Muay Thai, and has since earned a black belt in Brazilian Jiu-Jitsu. However, his bread and butter was his Muay Thai.

Vera went 2-0 on the regional circuit before entering the WEC heavyweight tournament. His surprising win brought him to the attention of the UFC. Vera won his first four fights in the Octagon, all via knockout in the first round. The last of those wins was against former UFC champion Frank Mir, which earned Vera a title shot. However, Vera went through a nasty contract dispute that left him sidelined for nearly a year, and he has never been the same since. Vera has gone just 4-7 (1 NC) since his amazing start.

4. Karo Parisyan

Karo Parisyan has to be one of the poster boys for unrealized potential. He had a lifetime of combat sports experience before ever joining the UFC. He began training judo under Gokor Chivichyan when he was just nine years old. By the time he was 10, he was starting to cross-train in judo, sambo, catch wrestling and Greco wrestling under Chivichyan and the legendary Gene Lebell. Parisyan won six National Junior Judo Championships, medaled in a number of international competitions and competed in the Olympic Judo trials. He also was a BJJ black belt and national champion before turning his sights on MMA.

Parisyan started his career by going 9-2, with both of his losses coming from Sean Sherk. That’s when the UFC came calling. In his second UFC fight, Parisyan lost to Georges St-Pierre, though he took him the distance. He then won the WEC welterweight title, but vacated the belt to return to the UFC. After picking up three more wins in the UFC, Parisyan was scheduled for a title fight. Unfortunately, an injury forced him to miss his chance. Upon his return, he remained near the top of the rankings for the next three years while compiling an overall record of 18-5. Then, Parisyan had to pull out of a fight due to a back injury. That was the beginning of the end.

Parisyan returned to face Dong Hyun Kim. Parisyan won the fight, but the result was changed to a no-contest when Parisyan tested positive for prescription pain medication. Parisyan’s teammates and friends told the media he was dealing with an addiction to the medication following back and hamstring injuries. After serving a suspension, Parisyan pulled out of his next fight the day before weigh-ins, saying he was dealing with anxiety issues. Since the back injury, Parisyan has gone an unremarkable 4-5 with the one no-contest. His years as a top fighter seem long in the past.

3. Pedro Rizzo

Pedro Rizzo is a man who had the potential to be a legend, but today he is barely remembered by current fans. “The Rock” is a Brazilian Jiu-Jitsu black belt, but he trained under Marco Ruas and adopted Ruas’ pension for throwing brutal leg kicks. He was big, strong and possessed knockout power.

Rizzo started his career by going 9-0 with eight stoppages (five knockouts, three submissions). He showed such great potential that the UFC invested a huge amount of money (for the time) in his contract and in marketing him. However, Rizzo struggled in big fights. He was matched against Kevin Randleman for the heavyweight title and lost. Rizzo rebounded nicely with knockout wins over Dan Severn and Josh Barnett to earn another title shot, this time against Randy Couture in what turned out to be an all-time classic fight. Couture won a razor-close decision in a fight that seemed to break Rizzo. In an instant rematch, Rizzo lost easily when he was stopped for the first time in his career. Prior to the second Couture fight, Rizzo was 11-2 with 10 stoppages in his wins and had never been stopped. Since that fight, he is 8-9 and he has been knocked out seven times.

2. Mirko “Cro Cop” Filipovic

Mirko “Cro Cop” Filipovic was one of the biggest UFC free agent signings of all-time. He was expected to come in and take the UFC’s heavyweight division by storm. The hype and excitement around Cro Cop’s signing was not unwarranted. He started his career in K-1, where he accumulated 16 wins, was the runner-up in two K-1 Grand Prixs and topped noted legends and stars such as Peter Aerts, Jerome Le Banner and Remy Bonjasky. While Filipovic was competing in K-1, he also began his MMA career in Inoki Bom-Ba-Ye and Pride FC, where he racked up a record of 21-4-2. His MMA dominance was shown in the fact that he did not debut until Pride 17, but compiled the third most victories (18), the most finishes (16) and the second most knockouts (14) in Pride history. He remains the only man to defeat three former UFC champions in a row. Cro Cop also had just cemented his legacy by winning the Open-Weight Grand Prix when he hit the free-agent market.

Filipovic’s skill set was highlighted by the fact that he was one of the best strikers in MMA, with knockout power in both hands and feet. However, Cro Cop was not limited to keeping the fight standing. He trained for years with ground experts such as Fabricio Werdum to round out his skills. He has only been submitted once in his career, and that was courtesy of Antonio Rodrigo Nogueira nearly four years prior to his UFC debut.

Despite all his skills and accolades, Filipovic never panned out in the UFC. He was matched against little-known Gabriel Gonzaga in his second UFC fight to determine who would earn a title shot. Gonzaga was considered a ground specialist, and Cro Cop was heavily favored. In one of the biggest upsets in MMA history, Gonzaga completely knocked out Cro Cop with Cro Cop’s own specialty, a head kick. After that bout, the Croatian never looked comfortable and seemed hesitant to engage. Even when matched against fighters who would likely keep the fight standing, Cro Cop appeared tentative. With Cro Cop hesitant to pull the trigger, he struggled to find wins. Cro Cop went just 4-6 in the UFC and never lived up to the potential shown earlier in his career.

1. B.J. Penn

It may be a surprise to many to see B.J. Penn make an appearance on the list of those fighters who never lived up to their potential. After all, Penn is one of only two fighters to win UFC titles in two different divisions. He also is arguably the best lightweight of all time. The problem is that Penn should be in the discussion for the greatest fighter of all time, regardless of division. He has more natural talent in his little finger—which he can probably use to submit you—than most fighters have ever dreamed of having.

Penn’s nickname, “The Prodigy,” refers to his seemingly effortless ability to quickly learn, develop and excel. He earned his black belt in Brazilian Jiu-Jitsu in less than four years, something unheard of for an accomplishment that takes many over a decade. However, it was not like Penn was just given the belt. He earned it by medaling as both a blue belt and a brown belt in the World Jiu-Jitsu Championships. Penn proved he was worthy of the black belt by becoming the first American to ever win the World Jiu-Jitsu Championships as a black belt.

Shortly after winning the World Championships, Penn entered MMA, where everyone expected him to be a ground ace following in the tradition of the Gracies. However, Penn had other ideas. He showed off his striking prowess and power by knocking out each of his first three opponents in the first round. This unknown wrinkle in Penn’s game made him one of the most feared fighters in the sport. When mixed with his submission skills, his uncanny flexibility and solid boxing technique, his knockout power made it appear that Penn had no weakness.

Unfortunately, he did have weaknesses. They were never physical, but rather mental and motivational. He never seemed to care about winning as much as other fighters or his fans did. He appeared to hate training and dieting. Penn may be motivated for a fight or two, but soon enough his love of junk food, surfing and the beach take over. This lack of focus caused Penn to be void of the cardio needed for long fights and forced Penn to fight at weight classes that did not fit his frame.

A quick look at Penn’s career showcases this point. At lightweight, where he has to train hard to keep his weight under control, Penn was a remarkable 11-1-1 prior to his last two fights in the weight class against Frankie Edgar (one of those two fights ended in a controversial decision, Penn looked completely uninterested in fighting in the other). In all other weight classes, he is an unimpressive 5-6-1. Fans and media still talk about how dangerous a “focused Penn” is, but no one is willing to bet on when a focused Penn will show up.

Photo: B.J. Penn (Dave Mandel/Sherdog)

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About The Author

Richard Wilcoxon
Staff Writer

An East Coast native, Richard Wilcoxon grew up a die hard fan of traditional team sports. In the early 1990's, he stumbled onto the sport of MMA and has been hooked ever since. He started writing about the sport on his Sporting News member blog in 2005 where he worked to spread his passion for the sport. He eventually became an official staff writer for Sporting News' "The Rumble" MMA/boxing blog before joining The MMA Corner.