Former undisputed cruiserweight champion Oleksandr Usyk will be keeping both eyes on the year-end rematch between Andy Ruiz and Anthony Joshua.

Last month, at Madison Square Garden in New York City, Ruiz dropped Joshua four times to secure a seventh round stoppage and the WBO, IBF, IBO, WBA heavyweight titles.

Joshua has exercised a rematch clause and the second contest is being targeted for a date in December.

Usyk vacated his four world titles and made a move to the heavyweight division.

A planned heavyweight debut earlier this year was pushed back after Usyk suffered a training camp injury. The bout with veteran Carlos Takam will now take place on a date in the fall.

Even without a single heavyweight fight, the WBO has already made Usyk the mandatory challenger to the Ruiz-Joshua rematch winner.

"I'm very grateful that they made me a mandatory challenger. I know that it doesn't happen for no reason. They have nowhere to go. Everything is already set up in place," Usyk told Sky Sports.

"All we need is to just wait for the events to happen and I will definitely be boxing with one of them."

Usyk rejects some of the claims that Joshua lost because he has issues with shorter fighters. But if that's really the case, then Usyk believes Joshua will have a serious problem in the second fight,

"I don't think that's the reason [that Joshua lost to Ruiz Jr]," Usyk said.

"There is a general problem that takes place. It doesn't matter whether your opponent is tall or short. It doesn't matter whether you fight a two-metre tall guy, or a 1.80m guy. You are preparing with sparring partners that look exactly like your opponent. If he really has a problem with boxing with short people, then it's a really big problem."