The UFC featherweight champion suffered his first loss in the promotion after Diaz stepped in on eight days’ notice to shock the Dubliner via a second-round rear-naked choke in their welterweight bout in March.
The loss saw McGregor’s rise to stardom come to a sudden halt having claimed the 136-pound crown with a stunning 13-second knockout of long-reigning champion Jose Aldo last December.
But McGregor has promised a memorable encounter at the T-Mobile Arena at UFC 202.
“Fans can look forward to a ferocious fight,” he said . “I’m going in there with ruthless intention. They can look forward to an improved athlete, a focused athlete. It’s going to be one hell of a fight.”
The 28-year-old was initially set to fight then-UFC lightweight champion Rafael Dos Anjos in a unification clash at UFC 198 but the Brazilian was forced to withdraw due to a broken foot.
With Aldo and Frankie Edgar both declining the opportunity to replace Dos Anjos, McGregor decided to step up two weight classes to fight the American.
Many had questioned McGregor’s decision to face the naturally bigger Diaz but the Irishman believes size had no bearing on their first fight.
“I don’t feel the size was the reason,” he told BT Sport. “I can’t say move down a weight, I’ll get you there. What kind of fighter is that?
“He’s gotten even bigger than the last fight so I’m facing an even bigger man. But you know what, I’m excited about that and I’ve put in the correct preparation for that. I’ve sparred middleweights, fresh middleweights. The first fight was at 170 and my heart wouldn’t let me have it any other way.”
Pictures of McGregor training with Real Madrid star Cristiano Ronaldo surfaced online as the Irishman looks to expand his worldwide fanbase. Ronaldo joined McGregor during his holiday after helping Portugal win Euro 2016 earlier this summer.
McGregor was quick to praise the forward’s work ethic when asked about their time together.
“He’s a good friend of mine, I’ve been talking to him for a long time,” he said. “He messaged me on Instagram a while back because I was wearing his (CR7) underwear during the weigh-in for the (Diego) Brandao fight.
“But he’s a nice guy, he’s in some shape. He went more abs, I went more lats. I’d slap the head off him but he’s a very nice guy and he was in tremendous shape, he’s a true athlete.”
Watch the full interview with Conor McGregor tonight from 9.15pm on BT Sport 2. UFC 202 - McGregor v Diaz 2 - is exclusively live on BT Sport 2 this Sunday from 1am. Visit www.btsport.com/ufc for more info.