Belfast's Kevin O'Hara will now challenge Ricky Burns for the Commonwealth super-featherweight title in Glasgow on June 19.
Sweetpea is a replacement for Steve Foster Jnr, who has withdrawn from the Bellahouston Sports Centre show.
"It doesn't make any difference to me who I fight," said Burns, who makes the third defence of his title in front of the Sky Sports cameras.
"I was going to knock out Steve Foster Jnr, and now he's run away, I'll knock out Kevin O'Hara instead.
"I'm just glad that someone has got the balls to face me because Kevin Mitchell has been running like a big girl as well."
O'Hara, 27, has a 16-4 record and has never been stopped.
He was in action on Friday night in Belfast, winning on points over six rounds, and has won his last three fights.
The Ulsterman has fought in Glasgow before, narrowly losing to Willie Limond on points over 10 rounds in a challenge for the Celtic super-featherweight belt.
"I've been chasing an opportunity like this for a while," said the John Breen-trained fighter.
"Burns is a talented fighter but I've been watching him for years and I've worked out exactly how to beat him.
"I've not had a big fight for a couple of years, but this is my chance to gatecrash the domestic scene and I'm planning on taking it."
Tickets, priced at £30 and £50, are available from Frank Warren Box Office 01992 505 550, Ticket Scotland 0141 204 5151, Morrison Boxing 0141 554 7777.
