Watch: Ref 'almost kills' MMA fighter in Legacy FC

Legacy FC 56 came far too close to ending in tragedy.

Former Legacy Fighting Championship bantamweight title holder Manny Vazquez was defending his title against Steven Pearson in Dallas, Texas on Saturday.

As the bout approached the fourth round, both fighters had dished out their fair share of solid shots, making the judge's job incredibly difficult should it go the distance.

Fortunately for the judges, the bout ended in the fourth round. Not so fortunate, however, was how Pearson ended it - and it nearly cost Vazquez more than just the fight.

As the pair wrestled on the canvas, Pearson was able to lock in a rear-naked choke hold on his opponent, putting him to sleep almost immediately.

Warning: The video below contains disturbing images.

However despite Vazquez's clear lack of consciousness, the Legacy FC referee failed to step in immediately and stop the fight.

The 22-year-old unconscious fighter can be seen convulsing while still locked in the choke hold.

The incident sparked outrage among fans, who left frustrated comments on the video.

"Seriously, if that guy refs another fight the commission should be disbanded," one user said.

"That's not 'on the fighter'...The ref has one job," said another.

"I'm pretty sure he goes limp 3 seconds into this (video). At the very least the ref should have checked his arm then. This is scary," another user wrote.

Live fight commentators seemed equally concerned at the time of the submission.

"He's cranking hard," one commentator said. "He's going out. Is he going out?

"He's out, he's out, he's out. The referee has got to stop it."

Even after the ref broke Pearson's grip, Vazquez looked to be in a bad way, lying motionless on the canvas with his eyes rolling back in his head. While the footage stops at that point, there are no reports to indicate that he had not recovered positively after the fight.