The UFC's 20 Most Improved Fighters

"Evolution."

Make no mistake, the term is a fitting title to the UFC’s new pay-per-view opening montage. As the sport of mixed martial arts continues to grow and expand, its combatants are improving and maturing along with it.

From cagey veterans who have held belts in other promotions, to rising contenders just beginning to make their mark inside the famed Octagon, every fighter in today’s MMA landscape is forced to learn and drill techniques day in and day out to keep up with their opponents.

While many of the sport’s champions are naturally-talented athletes, they have put in countless hours in the gym to get to where they are. Let’s take a look at some of the fighters who are taking steps toward the next level.

Rob Tatum is a featured columnist for Bleacher Report MMA. You can also find Rob’s work at TheMMACorner.com.  For anything related to MMA, Follow @RobTatumMMA.

Michael McDonald

Bantamweight Michael McDonald's first professional bout came at the age of 16 years old. Since then, the fighter has reeled off wins in 14 of 15 fights, with his last four coming under the Zuffa banner.

In his Octagon battles, McDonald has showcased both precise kickboxing and strong grappling. The 21-year-old has claimed fight bonuses in two of his last three fights, quickly propelling him up the 135-pound ladder.

The Californian will face a significant test in his next fight, as he meets former WEC kingpin Miguel Torres at UFC 145 in April.

Chan Sung Jung

When the now-defunct WEC promotion made its only appearance on pay-per-view in April of 2010, few expected Korean import Chan Sung Jung to steal the show. The featherweight was making his promotional debut on the event's undercard, but when his fight was over, "The Korean Zombie" was a household name for MMA fans.

Following that battle, Jung was on the wrong end of a highlight-reel knockout at WEC 51 and with the UFC absorbing the promotion, his future looked bleak.

However, the Korean showed his resolve, taking the promotion by storm.

Jung executed the first "twister" submission in UFC history in a rematch with Leonard Garcia (who took victory in the WEC 48 bout) and followed that with a blistering seven-second knockout of former title challenger Mark Hominick.

With his two consecutive wins, Jung has shown that has grown as a fighter and is ready to be mentioned as a legitimate challenger to Jose Aldo's featherweight belt.

Jimy Hettes

Admittedly, it might be a bit of a stretch to call Jimy Hettes one of the most improved fighters in the UFC.  After all, Hettes has never lost in his 10-fight career.

What Hettes has done is put the UFC's featherweight on notice. With an arsenal of grappling and submission skills matched by few at 145 pounds, Hettes has managed to run through Ultimate Fighter veterans Alex Caceres and Nam Phan in his two Octagon bouts.

Hettes' dismantling of Phan produced the rarely seen 30-25 score on two of the scorecards. That sort of domination is a testament to Hettes' ever-improving skillset.

Look for big things from the 24-year-old in 2012.

Benson Henderson

Lightweight Benson Henderson's first year under the UFC banner made it very clear that he's out to erase any lasting memories of his last WEC outing. Henderson not only lost his 155-pound title at the promotion's last event, but he was on the wrong end of one of the most famous highlights in MMA history, Anthony Pettis' "Showtime" kick.

Since that time, Henderson has run ragged through one of the UFC's deepest divisions. Mark Bocek was the first fighter in Henderson's path and it was clear when the fight was over that Henderson was a changed man since falling to Pettis. Henderson has exhibited new-found aggression to complement his wrestling and grappling skills.

Dominant victories over contenders Jim Miller and Clay Guida have earned the Arizona-based fighter a crack at UFC gold. He'll take on divisional kingpin Frankie Edgar at UFC 144 on Feb. 25.

Nate Diaz

While Nate Diaz's older brother Nick has been stealing most the headlines of late, the younger Diaz is quietly making noise in the UFC's lightweight division.

After winning The Ultimate Fighter, Diaz struggled with consistency, even moving to the 170-pound welterweight division for a time before returning to his natural weight class.

Return he has; he's scored huge wins over former Pride champion Takanori Gomi and WEC stalwart Donald Cerrone in the past six months.

Trash-talking aside, Diaz has revealed a calmer, more focused attack and the results speak for themselves. Next on his plate will be consensus top-10 fighter Jim Miller on May 5 at UFC on FOX 3.

Danny Castillo

Lightweight Danny Castillo may not get the recognition of his Team Alpha Male teammates Urijah Faber or Joseph Benavidez, but the former WEC competitor has made continual improvements in his fight game since joining the UFC.

During that time, Castillo has won three of his last four fights, mixing his bread and butter (wrestling) with a relentless ground-and-pound attack. Fighting twice in just two months, Castillo dispatched of both Anthony Njokuani and Shamar Bailey to cap off 2011.

Next on his plate? Another strong wrestler in John Cholish on May 5.

Evan Dunham

After Evan Dunham dropped back-to-back fights to Sean Sherk and Melvin Guillard (the only losses of his career), many questioned whether the Oregon native had what it takes to compete with the elite of the lightweight division.

Two fights later, there is little doubt.

Dunham peppered TUF alum Shamar Bailey for three rounds with high-level boxing and then battered wrestler Nik Lentz en route to a TKO win in his most recent outing.

In each win, Dunham regained the confidence and cage generalship that he held prior to the losses. Now the fighter is in prime position for a title run at 155 pounds.

Seth Baczynski

Following a stint on season 11 of The Ultimate Fighter and a loss to fellow TUF alum Brad Tavares, Seth Baczynski was released from the UFC in 2010.

Rather than continue competing at middleweight on the regional scene, Baczynski moved down to the 170-pound welterweight division. He hasn't looked back since.

Now riding a four-fight win streak (including two straight since rejoining the promotion), Baczynski is ready to make waves in his new weight class. At 6'4", he is one of the largest competitors in the division and his slick submission game has spelled doom for both Matt Brown and Clay Harvison in recent outings.

Carlos Condit

The freshly-crowned interim champion of the welterweight division, Carlos Condit, is used to winning.

After the WEC's 170-pound division was folded into the UFC, Condit's championship status was quickly derailed in a decision loss to Martin Kampmann (his only defeat in nearly six years).

Since that loss, Condit has climbed back atop the rankings with champion and teammate Georges St-Pierre out of action.

In Condit's knockout wins over Dong Hyun Kim and Dan Hardy, the New Mexico-based fighter showed aggressiveness and a killer instinct that he lacked for his first few Octagon bouts. Those wins propelled him to a title fight with Nick Diaz.

Against Diaz, Condit showed a different part of his fight game: patience. Condit avoided getting pulled into a firefight with Diaz and took home a decision win and the belt.

Jake Ellenberger

Much like the aforementioned Carlos Condit, welterweight Jake Ellenberger dropped his first Octagon appearance, perhaps fittingly to Condit.

And like Condit, Ellenberger hasn't lost since. Now on a five-fight streak, the Nebraska native is poised for title contention. His ever-evolving striking offsets his wrestling and allowed Ellenberger to lay waste to former Strikeforce champ Jake Shields in less than a minute.

Now standing in Ellenberger's path to the belt is Ultimate Fighter winner Diego Sanchez on Feb. 15, when the UFC debuts on FUEL TV.

Johny Hendricks

Few fighters in MMA have the wrestling accolades of welterweight Johny Hendricks.

Whether it's the two national championships or the four All-American honors, few can argue with his credentials. That's what makes his fast rise to the top of the 170-pound division all the more impressive.

In just four years, Hendricks is already in title talk. His seven career knockouts have proven that he's more than just a wrestler.

Since falling to Rick Story in late 2010, Hendricks has been on a tear—twice scoring violent left hook finishes of his opponents.

The most impressive? A 12-second shellacking of perennial top contender Jon Fitch at UFC 141. The loss was only the second of the last nine years for Fitch.

Now Hendricks awaits his fate in one of the UFC's deepest divisions.

Tim Boetsch

While competing at light heavyweight, Tim Boetsch failed to truly establish himself as anything special in the UFC.

After alternating wins and losses over two separate stints with the promotion, Boetsch decided to move to the middleweight division. He's likely wishing he had done it sooner.

Boetsch has manhandled former Ultimate Fighter combatants Kendall Grove and Nick Ring since moving to 185 pounds. By utilizing his size and strength, Boetsch has been able to dictate where the fights take place and has cruised to victory in both of his appearances in the division.

In the UFC, however, the road is never easy. Next up for Boetsch is a clash with former title challenger Yushin Okami at UFC 144 on Feb. 25.

Ed Herman

When middleweight Ed Herman's knee buckled underneath him at UFC 102, some speculated whether the TUF alum would ever be the same.

After nearly two years of rehabilitation and a transplant to Colorado, Herman has answered the question emphatically. He's definitely not the same—he's better.

Herman has made short work of fellow TUF competitors Tim Credeur and Kyle Noke—Credeur by KO, Noke by submission.

Building off the momentum, Herman handed undefeated wrestler Clifford Starks the first loss of his career at UFC 143, scoring yet another submission win.

Mark Munoz

Easily one of the biggest success stories of dropping weight classes, middleweight Mark Munoz has worked his way into title contention at 185 pounds.

Another decorated wrestler with a national championship on his resume, it's the striking of Munoz that has aided his ascension up the ladder.

Carrying an impressive record of 7-1 since the move, including four stoppages due to strikes, the heavy-handed fighter was slated for a No. 1 contender fighter in late January before an elbow injury put him on the shelf for the near future.

Chris Weidman

Much like featherweight Jimy Hettes, middleweight Chris Weidman carries an unblemished record in MMA and the UFC. And similarly to Hettes, every time he sets foot in the Octagon, he makes his mark on the division.

In three of the former All-American wrestler's four UFC bouts, he's fought on short notice. And each time, he's left the cage with an impressive win.

Undoubtedly, Weidman's most recent outing was the biggest of his young career. Stepping in on just 11 days notice, Weidman was able to defeat former title challenger Demian Maia live on network TV.

After the big win, it's hard to say just how high Weidman's ceiling might be.

Rashad Evans

A former champion improving? In the case of Rashad Evans, absolutely.

When Lyoto Machida handed Evans the only loss of his career at UFC 98 (and taking the light heavyweight strap in the process), Evans was forced to evaluate his attack and game plan.

What resulted was a conservative fighter that frustrated both fans and UFC President Dana White. Despite wins over Thiago Silva and Quinton "Rampage" Jackson, Evans struggled to earn another shot at the 205-pound strap.

However, when teammate Jon Jones earned the belt, things changed dramatically for Evans. He switched gyms, joining Imperial Athletics in Florida. There, he regained his edge, easily dismantling Tito Ortiz in August of last year.

In his most recent fight, Evans, although not as aggressive, cruised to a win over previously unbeaten Phil Davis. Now he'll face Jones for the belt at UFC 145 on April 21.

Alexander Gustafsson

Carrying a 13-1 record (5-1 in the UFC), it's hard to believe that Swedish light heavyweight Alexander Gustafsson is just four years into his MMA career.

The towering European has finished all five of his UFC wins and has only seen the judges' scorecards once in his career.

His only loss came to fellow 205-pound contender Phil Davis, who outwrestled the Swede and eventually submitted him.

Gustafsson would bounce back with a vengeance, scoring two submissions and two TKOs since, including impressive wins over strong wrestlers Matt Hamill and Vladimir Matyushenko.

He'll face another big test on April 14 as he takes on Brazilian Antônio Rogério Nogueira at UFC on FUEL TV 2.

Pat Barry

First off, let's be clear: Pat Barry's base is and always will be his kickboxing. The heavyweight possesses some of the most lethal leg kicks in all of MMA.

The alarming aspect of Barry's 4-4 record inside the Octagon is the three submission defeats, including an embarrassing rear-naked choke to vaunted striker Mirko "Cro Cop" Filipović.

That aside, there is light at the end of the tunnel for Barry. He's only 11 fights into his career. In his last fight against Christian Morecraft, Barry found himself in multiple bad spots on the mat, but survived. His armbar escape showed great technique and led to his eventual knockout win.

While it's unlikely we'll see Barry score a submission win of his own any time soon, he's exhibiting time on the mat between fights. Next up for the Louisiana fighter is Lavar Johnson on May 5.

Mark Hunt

Mark Hunt may be the original Pat Barry. The Samoan's record and background are nearly identical, only he's been doing it longer.

Like Barry, Hunt's pedigree is kickboxing, even claiming a K-1 Grand Prix in 2001.

As he transitioned to MMA, his powerful and crisp technique led him to victory over legends Mirko Filipović and Wanderlei Silva before the chink in his armor was discovered.

Hunt was submitted in five of six bouts between 2006 and 2010. Surprisingly, the UFC brought the veteran back for another chance. The heavyweight has taken advantage.

A vicious knockout of Chris Tuchscherer revitalized Hunt's career, earning him a main card bout at UFC 135 against Ben Rothwell. Hunt dominated Rothwell, and managed to attempt an armbar, something many thought they'd never see.

Although his time in the sport is likely limited due to his age (37), Hunt will get a chance to move up the ladder against Cheick Kongo at UFC 144 on Feb. 25.

Fabricio Werdum

While Brazilian Fabricio Werdum is easily one of the most decorated Brazilian Jiu-Jitsu practitioners on the planet, it's his recent display on striking that should have the rest of the UFC heavyweight division concerned.

Werdum was famously knocked out at UFC 90 by current champion Junior dos Santos and left for Strikeforce. But when the promotion was purchased by Zuffa, Werdum found himself back in the Octagon.

Just one fight in, it's clear that Werdum is serious about challenging for the title. Utilizing brutal muay thai knees (learned under the tutelage of Rafael Cordeiro at King's MMA), Werdum battered Ultimate Fighter winner Roy Nelson for three rounds.

With Dos Santos facing Alistair Overeem (the last man to defeat Werdum) this summer, Werdum quickly established himself as a potential challenger for the winner sooner rather than later.