Undefeated McGregor (11-0, 9 KOs) faces Ruiz (23-4, 12 KOs) as part of the stacked card headlined by Danny Dignum’s WBO European middleweight title defence at York Hall in London this week, which will be broadcast live in the US on ESPN+ in association with Top Rank, and worldwide on IFL TV.
It's the first time that 'Lightning' has been back in the ring since August, and the Edinburgh sensation wants to win in impressive style to potentially set up an eliminator for the IBF bantamweight title in his next fight.
McGregor said: "I've been inactive for a while so I needed to get back in the ring and fight. Ruiz is well known, tough and durable, but I want to go in and make a statement and do it in a devastating way.
"I've been progressing fast, and I feel I have proven I'm at European and world level. Going off the number of fights I've had you would maybe think I shouldn't be there, but I'm not scared to take those risks.
"I think that's why I have achieved so much so early in my career. I'm fearless and nothing will faze me. I want to be involved in the big fights. I'm confident that my next fight after this will be an eliminator for the IBF title.
"I've already accepted offers to fight some of these guys the IBF were ordering me to fight, but for some reason they aren't materialising. I'll just keep busy and stay sharp, and hopefully after this fight I'll be in a good position.
"There are some big names in the division, but what have I got to lose? I will fight my heart out and give everything. Some people might be afraid to lose their 0 and that's why they won't take certain fights, but I'm not scared of anything.
"Training has been going great, and we've got a tight group full of unbelievable talent. We're always pushing each other to the limits, and training with people like Josh Taylor helps to get that extra 5% from me."
Elsewhere on Friday’s card, Bilal Fawaz makes his professional debut, Joe Giles meets Lewis van Poetsch, Paul Ryan takes on CJ Wood, plus Jordan Flynn and George Mitchell are in action.