After defeating Anthony Joshua, to most people's surprise, for the WBA, IBF and WBO titles back in June, Andy Ruiz Jr is putting the work in yet again for their upcoming rematch, much to the horror of AJ fans. 

The triple-champion held a public workout session in San Diego on Sunday, taking the opportunity to show off the incredible punches which helped him to topple Joshua earlier in the year. 

Ruiz pummelled the pads of his trainer Manny Robles with terrifying power, which has sent some Joshua fans into panic-mode, with a few already warning the Brit that he faces another devastating loss when the pair meet again for the rematch.

One user commented: "Would kill the average man."

Another said: "I hate to be on the end of that punch. Good luck AJ."

Someone else added: "That'll f***ing hurt, I'm glad I'm just a fan."

Ruiz has also been putting a tonne of work into losing weight and keeping fit, after he revealed that he wanted to drop 10lbs before he fights Joshua in December.

Many people are incredibly impressed by his fitness, with many agreeing with one user who said: "For someone as big as him, he's FAST! Hell, he's fast even without considering his size!"

However, some fans are not so happy about Ruiz's new shape, with former world champion Timothy Bradley previously expressing his concern about the Mexican-American's switch in tactics.

Speaking to Fighthype, as per The Sun, Bradley said: "I don't like the fact that Ruiz is changing his whole look and physique.

"I think that's going to hurt him. But I think he might speed up with the hand speed. It might speed up, but I'm worried about the power.

"I don't know if he's going to have the weight behind his punches anymore, and that's what he's going to need honestly.

"He just needs to be hungry. That's it, and be a dog. Be able to take the punches from Joshua, and dish it back."

AJ v Ruiz Jr is still currently scheduled for December 7 in Diriyah, Saudi Arabia.