One of the great things about the sport of MMA is constant change. There is always a new fighter gunning for a spot amongst the greats and a great fighter attempting to retain their legacy. The constant pressure forces fighters to change and adapt throughout their entire career.

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Fighters change their styles and weight classes, and they may even look completely different throughout their career. Some fighters may forge themselves anew and become their best selves through change, while others may crumble in the face of it. To be the best, a UFC fighter has to adapt to the high-level competition. But in doing so, they may risk their career and that risk makes the sport all the more interesting.

10 Charles Oliveira

Charles Oliveira initially started as a featherweight and a grappler in the UFC. He was considered a middling talent with lackluster striking who could not contend with the top guys. Early in his career, every time he faced up against a gatekeeper talent in the UFC, he lost.

He turned it around, honing his striking skills and becoming one of the best strikers, hopping up to his more natural lightweight division. He has since been on an insane run, winning his last 10 fights, nine of them by finish, and claiming the UFC Lightweight Title.

9 Anthony Johnson

The modern fighter Anthony Johnson is a hard-hitting light heavyweight/ heavyweight and just in general a very large man, but the most surprising thing about him is where he started in the UFC.

Originally a welterweight, Johnson struggled to make weight throughout his early career. After having multiple catchweight bouts, he was cut from the UFC and came back later on as a light heavyweight.

8 Jared Cannonier

In a reverse of the Anthony Johnson story, Jared Cannonier originally joined the UFC as a heavyweight. Through training and a better understanding of nutrition, Connonier has found his more natural weight class.

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Now fighting as a middleweight, Cannonier still maintains that heavyweight striking power but in his more natural weight class.

7 Wanderlei Silva

A long career in the fight game is due to take its toll on any fighter. This is probably more evident in the case of Wanderlei Silva than in most other fighters.

After getting his nose broken so many times, Wanderlei opted to get plastic surgery on his face to allow for better breathing through his nose. This drastically changed his appearance halfway through his career. The doctor also scraped away a significant amount of scar tissue from Wanderlei's face, giving him a drastically different appearance.

6 Dustin Poirier

Change may not always be evident in terms of looks or size. Sometimes it comes down to stylistic choices a fighter makes to improve their career.

Dustin Poirier originally was a brawler with a lack of respect for opponents. He would charge in guns blazing, looking to finish the fight. He has since crafted a defensive-minded technical kickboxing approach to fighting that makes him one of the best lightweights in the world

5 Vitor Belfort

There is a common joke around Vitor Belfort's career about which Vitor would be fighting, either normal Vitor or TRT Vitor.

Belfort has been known to play fast and loose when it comes to performance-enhancing drugs and in terms of physical appearance, it's a stark difference when facing TRT Vitor compared to normal Vitor.

4 Jake Collier

Another drastic weight change saw Jake Collier who began his UFC career at middleweight find his way up to heavyweight. The former middleweight has had an up and down career at middleweight, light heavyweight, and heavyweight.

He has yet to be able to string two wins together in the UFC but has also never lost twice in a row. This means that his UFC career has been a win and then a loss repeatedly over his 10-fight run so far.

3 Alistair Overeem

Change is bound to happen to any MMA fighter who has a lengthy career. No fighter has had a lengthy career in Kick Boxing and MMA like Alistair Overeem.

Starting MMA in 1999, over his 22-year career, we have seen Alistair grow up in front of us. Fighting some all-time greats along the way, Alistair's battle-scarred face is a long way from the fresh-faced boy he was when we first saw him fight.

2 Andrei Arlovski

Andrei Arlovski is another fighter whose longevity has changed him throughout his career. From the monster that was the terrifying heavyweight champ with the sharpened teeth mouthpiece to the UFC gatekeeper.

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Arlovski is now more of the father figure of the UFC's heavyweight division, using diligent striking and grappling control compared to his earlier career where he was considered a vicious striker.

1 Chuck Liddell

One of the more depressing changes that can happen to a UFC fighter is losing their chin. That's when a fighter who was once able to take every punch and continue to throw back now falters at some less significant strikes.

There is no fighter like Chuck Liddell in this category. He was seen as an unstoppable force that would walk down and knock out everyone in his way. However, during his later days, he was on the losing end of vicious knockout after vicious knockout. That was a truly sad way to see The lceman go out.