McGregor predicts quick knockout of Diaz

"His soft body and his lack of preparation, he will not be able to handle the ferocity. End of the first I feel he will be put away," McGregor told a news conference at the UFC Gym in Torrance, California.

"There's a respect there between us but it's business in there and business is business. He will be KO'd inside the first round."

McGregor, a featherweight champion who is unbeaten in seven UFC fights, was looking to make history against Dos Anjos by becoming the first fighter to hold titles in multiple weight classes simultaneously.

While admitting that not being able to fight for the belt stung, McGregor said he agreed to move up two weight classes to accommodate Diaz, who doesn't have enough time to drop weight, and because he only cares about his payday.

"I don't care about weight. It makes no difference to me. As long as there's an opponent and a date, you'll see me here. said McGregor. "The only weight I (care) about is the weight of them cheques, and my cheques are always super-heavyweight."

The verbal jabbing took a more serious tone when Diaz, sitting across from McGregor on a raised platform in front of an Octagon, randomly stated that everyone in the Ultimate Fighting Championship is on steroids.

McGregor shot back immediately: "Steroids? What are you talking about steroids? Don't be putting my name with steroids," he said. "I'm major against that. Don't put my name in the name of steroids, Nate."

Before the end of the news conference, which was open to the public and made up of a pro-McGregor crowd despite being held on Diaz's home turf, the Irishman belittled the injury to Dos Anjos.

"Dos Anjos has a bruise on his foot. Did ya see it? It's a bruise. Ice. Ibuprofen," said McGregor. "If I jumped under an X-ray, the doctor would slap me and say: ‘What are you doing, kid? Get out of here! Stop this.'"

(Reporting by Frank Pingue in Toronto; Editing by Larry Fine)