Brendan Schaub is finally firing back at his haters.

For several years, the former UFC heavyweight has consistently found himself on the receiving end of online hate comments from fans and fellow fighters.

The ex-fighter, who is now a comedian and podcaster, usually turns the other cheek, but he refused to do so after being insulted by Nate Diaz for no apparent reason.

Schaub and Diaz famously clashed backstage at Floyd Mayweather vs Conor McGregor in 2017 and now seven years later, their beef has seemingly restarted out of nowhere

On Friday evening, Diaz took to X - formerly known as Twitter - to give Schaub a new and unkind nickname that promoted a violent outburst from 'Big Brown'.

"Brendan the big ol p**** Schaub," Diaz tweeted.

Schaub lets a lot of things go unchecked, but he felt compelled to fire back at his former UFC colleague, who he challenged to a grappling match that he's confident would end with Diaz getting seriously injured.

"Oooh buddy. I prob got 20lbs on you so not too far off," he replied.

"I'll snap your neck. Set up a grappling match and let me know how it goes for you. Have one of your handlers read this tweet and get back to me."

The 41-year-old upped the ante by sharing his response to Instagram and adding a caption that speculated about what may have prompted Diaz to insult him out of nowhere.

Schaub also doubled down on his grappling match proposal.

He wrote: "Not sure what set this dude off. Mentioning CTE I assume.

"All good. Do something about it bud. I'm not hard to find. Have your handlers set up a grappling match. Let's see how it goes for you."

In December 2014, Schaub walked away from MMA after being dominated in a TKO loss to Travis Browne a few days before his friend and UFC commentator Joe Rogan staged an infamous intervention on his podcast.

A decade later, the former heavyweight contender is glad that he retired.

Schaub recently got emotional while discussing his former sparring partner Shane Carwin, who has struggled financially since ending his UFC career in 2011.

Despite boasting a degree in engineering, Carwin has been unable to hold down a job as he has been experiencing symptoms linked to CTE (chronic traumatic encephalopathy), a neurodegenerative disease caused by repeated trauma to the head that can only be detected from an autopsy.

A few days later, Schaub revealed that he turned to a massive fight offer.

Jorge Masvidal approached him about doing a bare-knuckle MMA bout.

Not keen, Schaub claimed he would end his retirement, but only for an 'outlandish' amount of money, which left him in a strange spot when it was immediately agreed to by 'Gamebred'

Still, the American heavyweight turned it down. Schaub told MMA reporter Damon Martin that he doesn't want to take any more punches to the head and doesn't need to be 'Elon Musk rich'.

It is currently unclear exactly what caused Diaz to insult Schaub in such a way.

Only time will tell if the two men will settle their differences on the mat.