Andy Ruiz Jr has sent a reminder to Anthony Joshua about the power that he possesses, although the Brit probably doesn't need reminding considering what happened in their first fight.The highly unfancied Mexican shocked the boxing world by defeating Joshua in New York back in June, flooring AJ four times on the way to a seventh-round stoppage.Though Joshua was stunned in Madison Square Garden a few months ago, he's still expected to comfortably gain revenge in Saudi Arabia on December 7.Ruiz Jr will no doubt have other ideas, though, and will relish being the underdog again in the desert.As preparations gather pace ahead of their much-anticipated rematch, the Mexican-American posted a video on Twitter of him sparring with trainer Manny Robles.

In an impressive display of power that we all now know he has, Ruiz Jr shows fast hands before smashing Robles' pad clean off.

He captioned the video: “Feeling good, camp is in full effect. My team and I are working hard one step closer to being ready for Dec 7th.”

Ruiz has also vowed to add the “missing belt” to his collection of unified titles after his AJ rematch.

He said: "Of course, I'm just missing one belt.

"One belt to be the undisputed heavyweight champion of the world and that's the goal, but I don't want to look past Anthony Joshua.

"I want to defeat him one more time, because there's a lot of critics saying that it's a lucky shot, that I'm going to lose.

“I'm using all the negative energy to positive energy, so we're going to win."

Boxing fans that saw Ruiz Jr's videos weren't convinced that he can deliver a second shock against Joshua though.

We will find out in December whether Ruiz Jr can do the unthinkable again or not.