Rory McIlroy has admitted he could be sidelined for the rest of the year and will "assess his options" with his medical advisors when he returns home after a disappointing PGA Championship.

McIlroy hinted after his third round at Quail Hollow that he was considering taking another break from the game as he continues to be hampered by the rib injury he first suffered at the BMW SA Open at the start of the year.

The world No 4 remains hopeful of competing in The Northern Trust - the first event of the FedExCup Play-Offs - in a fortnight, but he revealed his schedule for the rest of the season remains "up in the air".

Rory McIlroy admitted his main focus is already on next year's Masters

He stayed true to his word about finishing the final major of 2017 on a positive note and fired a four-birdie 68 to close on one over par, completing his tournament long before the leaders had teed off.

But as he faced the media afterwards, McIlroy admitted his focus was already on the Masters in April and that he would take another lengthy break from competitive golf, ruling him out of both the FedExCup and the Race to Dubai Final Series, if he felt he was unable to play at his best.

McIlroy fired his best round of the week on the final day at Quail Hollow

"I don't know what I'm going to do. You might not see me until next year, you might see me in a couple of weeks' time. It really depends," said the 28-year-old, who was out for seven weeks when he first sustained the injury, which he aggravated at The Players Championship in May and spent another month on the sidelines.

"Right now I can feel my left rhomboid going into spasm, and that's the way it has been the last few weeks. I have upped my practice coming into these two events because I wanted to feel like I was in a good place in my game.

"But right now it's a tough one because I go out there and shoot decent scores, but when I come off the course I feel my left rhomboid going into spasm, and the inside of my left arm goes numb. So I don't know what to do. I have got this next week off to assess what I need to go forward.

"It's not as bad as it was at The Players when it really flared up on me. But it's there and I can play 18 holes, but once I get done, having to go through the whole routine of getting it ready to go again the next day, you shouldn't have to do that. If I was injury-free, that wouldn't happen.

McIlroy was suffering post-round spasms as he spoke to reporters

"I'm flying home to Northern Ireland and I'll catch up with (trainer) Steve McGregor this week and see what we need to go going forward. But the more I play, it's just not allowing that time to heal 100 per cent."

McIlroy feels he has "a sense of duty" to defend the FedExcup title he won in spectacular style on the eve of the Ryder Cup last year, when he followed up his win at the Deutsche Bank Championship with a thrilling play-off victory over Ryan Moore at the season-ending Tour Championship.

But he added: "If I'm capable of playing, I feel like why shouldn't I? But then at the same time, if you are not capable of playing at your best, why should you play? So, again, it's a Catch 22. We'll see what happens. I'll assess my options in the next few days and see where we go from there.

McIlroy first suffered his rib injury in South Africa in January

"I feel like I'm capable and playing well enough to give myself a chance in it, but April is a long way away and that's the next big thing on my radar. I have a good bit of time to get healthy and address a few things going forward, so the next big thing is April and that's really what my focus will be on from now until then."

McIlroy also conceded he did not allow enough time for the injury to heal fully when he made his first comeback of the year at the WGC-Mexico Championship following a seven-week lay-off, although he insisted the problem was intensified when he went through extensive club-testing sessions after his wedding and subsequent honeymoon.

He aggravated the injury at The Players Championship in May

"An injury like this, it's eight full weeks of rest before you start to rehab it and then you go again," he said. "I felt like we took as much time as we needed to at the start of the year, that was basically seven or eight weeks. I got back playing and it felt okay through the Masters.

"I switched it off for a couple of weeks because I was getting married and going on honeymoon, but once I started practicing again, I didn't build up the volume gradually. I went from zero to hitting balls for three or four hours a day, and that aggravated it a little bit.

"I just haven't it allowed it the time to fully heal. I wanted to play the season and I feel like I'm capable of playing well and winning and putting rounds together. But if I want to challenge on a more consistent basis, I need to get 100 per cent healthy."