World number two Rory McIlroy will have an MRI test on his troublesome back in Belfast on Monday in an effort to identify the cause of his current discomfort.

Speaking at the Players Championship in Florida on Friday, McIlroy acknowledged that he had aggravated his back.

"I’ve been struggling with it a bit this week, sort of felt it for the first time on Sunday," the County Down man said after his one under second round with a birdie on the last saw him make the weekend cut.

"Then I've just sort of been managing it since. It's not, obviously not a hundred percent, but it's good enough to get myself around here for the next couple of days.

"I'm going for a MRI scan on Monday just to make sure it's not serious and then I'll see what we do from there."

McIlroy was speaking after a second-round 71 left him five strokes off the clubhouse lead at TPC Sawgrass.

Four-times major champion McIlroy has been dogged by back issues for several years, but he is optimistic this latest flare-up is not serious.

"Thankfully it feels more muscular than joint or bone at this point. I feel like I can distinguish what the difference is between the two," he said.

Meanwhile, former Master champion Danny Willett admitted his body and mind need a rest after being forced to withdraw from the €9.5m event,

"I've already limited the schedule down a lot, obviously all of the travelling we've been doing, and everything that's been going on," said Willet, who withdrew after nine holes of his second round.