Shocking video shows the incredible damage a UFC star suffered over 15 years of fighting

MMA fans and experts have expressed their concern over a distressing video of former UFC fighter Nam Phan which shows a marked deterioration in his speech over his career.

Phan, 41, is a retired American mixed martial artist and professional boxer who started competing professionally in 2001.

The Californian, who has competed in some of the biggest promotions on the planet including the UFC, officially hung up the gloves in 2017 but has still remained active by competing in boxing and Muay Thai events.

A video clip being circulated on social media shows a clear deterioration in Phan's speech throughout his career, likely caused by his many years of sparring and fighting.

The clip's earlier footage shows Phan when his speech is crisp and easy to understand, but in the more recent vision he appears to slur his words, have difficulty with pronunciation and talks very slowly.   

'Rough man. Nam is an OG,' commented one fan.

'Nam Phan was such a likeable fighter. I am sad to see him like this,' wrote another. 

Well-known MMA journalist Luke Thomas shared the video on Tuesday, commenting on the sad situation.

'Devastating,' he wrote.

'So many issues intersect with this, too: poor commission oversight, limited fighter pay, fighter's own risk assessment and more.

'This sport will absolutely break you. Lots more where this came from, too.' 

Some fans of the MMA star have suggested that Phan is suffering from the effects of the fatal brain disease chronic traumatic encephalopathy (CTE).

CTE is a degenerative brain disorder which has strong links to repeated head knocks, and can only be diagnosed after death.

It can lead to dementia, personality changes and suicidal thinking, and there is no cure or treatment.

In a recent interview Phan admitted that he would like to have a few more fights, but fans of combat sports don't want to see that. 

'He shouldn't be fighting anymore. It breaks my heart to hear him,' commented one fan.

'This is where commissions need to step in. This guy should NOT be fighting anymore,' replied another.

Last year, former UFC fighter Julie Kedzie revealed that she plans to donate her brain for post-mortem research.

Kedzie, 42, had 29 professional MMA bouts, with her final two coming with the UFC as she finished her career in 2013 with a record of 16 wins and 13 losses.

In the decade since, she has openly admitted to suffering with depression, anxiety, hyperactivity, impulsiveness and lack of sleep, which are all symptoms of the fatal brain disease chronic traumatic encephalopathy (CTE).

With this in mind, Kedzie has pledged to donate her brain after she dies so that it can be studied, and hopes the research can help other women in combat sports in the future.