UFC heavyweight champion Cain Velasquez has told Tyson Fury to prove himself in mixed martial arts if he wants to fight him inside the octagon.
The 30-year-old Californian was responding to a challenge put forth by Fury on Twitter.
"I challenge you to fight all in a cage or ring! It could be billed as the man vs midget. Let's get it on!" Fury tweeted.
Velasquez defeated Junior dos Santos for the UFC heavyweight title in September.
He said that anyone who wants to challenge him must first work their way up the ladder, and insisted that Fury is no different.
"I'm not a boxer," he said. "I'm a mixed martial artist, and if he wants to fight, he can go into the UFC and work his way up like everybody else does. Nothing is given to you in this world.
"To me, it's like don't talk about it, go ahead and do it. That's all I have to say about that."
Velasquez holds an 11-1-0 record in UFC.
