US PGA Championship 2015: Rory McIlroy says he needs to equal record low round to stand chance of claiming title for third time

The world No 1 came out smoking with two birdies and an eagle in his opening five holes

Rory McIlroy hits a drive on the ninth hole during the third round of the PGA Championship at Whistling Straits (AP)

Rory McIlroy is still dreaming big at the PGA Championship after a personal best of the week 68 in the third round took him to six under par.

The world No 1 trails leader Jason Day by nine strokes, and though he estimates he will have to equal the record low score for a major, 63, or even better it to retain the trophy he won for the second time a year ago, he claims the chase is on.

“I definitely believe it is out there for me. I feel I’m playing well enough to do shoot something like that (62). As long as I’m no more than ten shots back going into tomorrow, I feel with a great start again and trying to keep the momentum of the round going, there is no reason why I can go out and shoot 64 or 62 that I might need.”

McIlroy came out smoking with two birdies and an eagle in his opening five holes. His birdie putt at the first somehow defied gravity to stay up and he had a 10-footer for another at the third that drifted narrowly wide.

There is, however, nil room for error at Whistling Straits. He failed to get up and down at the sixth after missing the green with his blind approach and a bunker off the tee at the eighth cost him another bogey. There was more turmoil on the back nine but two birdies in the last three holes left him a hero’s shot at nirvana.

“It was a day that started well and ended well, birdying two of the last three holes. The stuff in between was a little patchy at times. I hit a lot of good shots, I putted better. There were just a couple of loose ones here and there. I came off the course definitely thinking there was a really low one there. It’s still my best score of the week, but it could have been a lot better.”