‘He tapped’: UFC legend Werdum stunned by bizarre KO defeat after claiming he was showing mercy by letting opponent escape (VIDEO)

Former UFC heavyweight champion Fabricio Werdum has cried foul play after his Professional Fighters League (PFL) debut ended in defeat, with the veteran claiming opponent Renan Ferreira tapped out before gaining a TKO victory.

In his maiden outing for his new employers, 'Vai Cavalo' started off well as the two combatants let off a series of flying kicks at one another.

Ferreira took top position, but Jiu-jitsu expert Werdum refused to yield on an armbar hold that later became a triangle choke.

Carrying on regardless, Ferreira powered through with a barrage of punches that eventually caused referee Keith Peterson to wade in and call a TKO stoppage.

Controversy took center stage and the shine off Ferreira's win when replays clearly showed that he tapped Werdum's shoulder while stuck in the triangle choke. 

"I think everybody saw the fight," the Porto Alegre native said in a post-fight interview, discussing how he had loosened his grip.

"He tapped and I have to respect my opponent. I have to stop. Maybe I [should have opted to] break his arm or put him to sleep.

"When he tapped, I automatically stop the fight but he kept going to punch my head. But I stopped because he tapped."

Asked whether he would appeal the result that cost him six points in the tournament, the 43-year-old wasn't entirely clear – but he has now filed one with the New Jersey State Athletic Control Board, according to his manager, Ali Abdelaziz.

The PFL will send the governing body the footage for review, but there is no doubt for Werdum that he was done dirty.

"In my mind it was over because I feel when he tapped my shoulder. This is why I stopped the fight," he said.

"I stopped and he keeps going to punch my head. The referee doesn't see nothing. When you tap, you have to stop the fight.

"But it happened and everyone saw he tapped for sure and he knows he tapped."

Onlookers laughed at the fact that Werdum lost his PFL debut to a guy who played him in a biopic of BJJ legend Fernando “Tererê” Augusto that is set to be released later this year.

Calling the scrap "crazy theater", others questioned why Werdum relented – but MMA practitioners explained that the seasoned veteran has been taught to do so when his opponent has clearly submitted.

Werdum also addressed the saga on Twitter. "I've been fighting for 23 years, and one of the first things we learn when your opponent gives up [is that] we have to respect [them]," he said.

While debate played out over social media and UFC welterweight title challenger Gilbert Burns demanded the result be overturned, one punter predicted that the controversy will "play out as a win for PFL".

"Ambiguous enough ending that they can gift him points to make the playoffs, yet it's generating 10 times the discussion a simple steamrolling — or even an uncontroversial upset — would have," they added.

"And if they meet again in the playoffs? Hoo boy."