McIlroy moves one clear

Starting from the 10th, the USPGA champion birdied three of his first six holes before an eagle at the 18th completed a back nine featuring six threes.

Another followed for birdie at the first and, though he dropped shots at the next two, successive birdies at four and five completed a good day's work for the 23-year-old from Northern Ireland.

The world No.1 is currently ranked fourth in FedExCup points race and would move to first if he goes on to win in Monday's final round. That would put him on course for a $10million bonus.

"Now that I'm in the tournament, I just want to play as well as I can and maybe reassess things going into the last day," world number one McIlroy said.

"But I was very happy with the two scores that I've got already and know that I need to go out and play just as good tomorrow to give myself a chance going into Monday.

Momentum

"I got off to a nice start and sort of just kept the momentum going. Everything seemed to work pretty well out there.

"I felt like I drove the ball a bit better today and hit more fairways, which gave me some more opportunities to make birdies, and I was putting well enough to take a few of those."

McIlroy is a shot clear of former Open champion Louis Oosthuizen, who added a 65 to his opening 66.

Tiger Woods shot a three-under 68 to be two shots off the pace, alongside fellow American Ryan Moore.

Woods blamed a cold putter for his mediocre round. "I didn't make anything today," he said, after missing all four of his putts between seven and 10 feet and three-putting the par-three 11th.

Overnight leader Noh Seung-Yul could not build on his opening 62 as he carded a level-par 71 to remain at nine under alongside four other players including Jason Dufner, who shot 66, and fellow round one high-flier Chris Kirk.