That doesn't sound great, obviously, but it also doesn't sound like it will affect his swing like the rib injury did a year ago.
A four-time major victor, McIlroy claimed the most recent of those at the 2014 US PGA Championship.
Health concerns aside, McIlroy sounded an extremely optimistic tone about once again establishing himself as one of the sport's top contenders, proclaiming: "Maybe before, I had to win from the front".More news: Game-by-game look at Alabama's season
McIlroy, 28, who was winless during an injury-plagued season last year, said he will have to undergo an echo cardiogram every six months and then an MRI scan every year. "Hey, I was planning on doing that anyway", he said. Let's just say that between now and when I signed off previous year, I feel way more optimistic, focused, motivated, purposeful. I've beaten them before.
Rory McIlroy has endured a variety of injuries over the years - from a severely sprained ankle that caused him to miss the 2015 British Open to a rib injury that knocked him off kilter for much of 2017.
"To be honest, I just went through the motions for the last few months previous year", McIlroy said.
"I don't care about the world rankings as I think about number of wins, the ability of the players against me, the number of majors the others have".More news: Wells Fargo Believes Johnson & Johnson (NYSE: JNJ) Won't Stop Here
He added, "I still feel that on my day, if I'm on my roll, and especially if I'm playing with them".
"That hasn't always been the case with me". I've seen what I have done in practice before, that I know I'm on track to where I want to be. I know exactly what I can do.
He will make his return at the Abu Dhabi Championship next week.More news: Bill Cosby references #MeToo movement after meal at Philadelphia restaurant