We've all heard of Ali v Frazier and Neymar v Cavani , but this sporting feud is a new one on us.
Golf star and Manchester United fan Rory McIlroy has revealed a dislike of former United midfielder Roy Keane which goes all the way back to when McIlroy was a child, all because Keane refused to sign an autograph for him.
Speaking about the importance of getting youngsters into sport, McIlroy revealed how exposure to their idols can shape young minds.
He said: “I remember going and watching the World Match Play at Wentworth every October, and getting golf balls from Mark O’Meara or Sam Torrance.
“And I remember how good I felt. But I’ve had it go the other way, where I asked someone for an autograph as a kid and they didn’t give it to me.
“And I’ve never liked him since.”
Then, when asked just who he was referring to, McIlroy spilled the beans.
“It was Roy Keane," he said, "who should be one of my heroes as a United player, but I’ve never liked him since.
“I went and asked for his autograph at the Portmarnock Links Hotel when he was with the Ireland squad, and he said no.
"It just sort of stuck with me I guess.
"So that’s why, if a kid asks me for an autograph, I always try to do it.”
McIlroy was then asked if he'd give Keane his autograph these days, saying: “Only if he gives me his!”
What do you reckon lads, settle it in the ring?
