He was replaced by Ruiz (21-2, 10 KOs), 25, of Argentina, who has won 10 fights in a row and looms as a likely more hard opponent for Conlan despite the lack of the revenge storyline Nikitin brought the promotion.
The incredible sold out event at Falls Park is main evented by Conlan facing the toughest test of his career so far when he takes on Ruiz, and will be live on BT Sport in association with Queensberry Promotions, and ESPN+ in association with Top Rank.
Michael Conlan is promising a career-best performance as he returns to action in Belfast this weekend.
Michael Conlan "I've had a target on my back since the amateur days".
"I know there's a lot at stake here yet I honestly feel zero pressure because I've done everything I can. I believe this is a coming out party for me and it's the best Michael Conlan you'll see". "I believe this is the first performance that I've performed at a certain level, but I've got more levels to go, and I believe I can be at that level".
I should have done it since the start of my career - it's making a big difference.
"I want to see the progression and want to see what Michael does in the gym when he's out in the spotlight", said Booth. "This is a special event, and my job is to ensure he does his job and that he performs how he's supposed to perform".
The fight was stopped due to a cut over Jenkins' left eye that was ruled to be caused by an accidental clash despite replays showing it was more likely caused by a punch landed from Gallagher.
"It's my favorite arena, and I love the atmosphere inside the arena and in New York City during fight week", Conlan said.
"I've done my homework on Keeler and I don't think he's ready".
"Boxing is a major part of Belfast, especially West Belfast". "It would be big anywhere in the United Kingdom or Ireland, but I'd love to have my first world championship fight at Madison Square Garden". "I suspect Ruiz will come forward but maybe not as aggressively as Nikitin was going to. The experience will be a big factor".
Conlan's older brother and Professional Development Coordinator with MTK, Jamie, says those are set to attend will enjoy a night like no other and has urged the fans to get in early and get behind all the local fighters on the card.