DUBLIN, Ohio — Whether it's his health or his personal life, Rory McIlroy is not easily distracted when he's on top of his game.
McIlroy made two eagles and three birdies on the back nine at Muirfield Village — along with a double bogey — on his way to 9-under 63 and a three-shot lead Thursday after the opening round of the Memorial.
A week ago, McIlroy began his week in England by announcing he and tennis star Caroline Wozniacki had broken off their engagement. Then, he went out and won the PGA Europe's BMW Championship for his strongest win in more than two years.
At the Memorial, McIlroy caught his spikes in the turf on his second shot at the seventh hole and felt pain the rest of the round, especially when he had to put a little extra pop into tee shots or long irons. He was limping when he walked off the stage after talking about how he made five birdies and two eagles after hurting his knee.
It was the lowest opening round in 39 years at the Memorial.
"I don't think it's anything more than just being confident with my game," McIlroy, 25, said. "I was expecting this to happen. I've been playing well. I've been posting good numbers, good rounds. And I knew my game was close. And honestly, I don't think it's anything to do with what's happening off the golf course. It's just I've been trending in the right direction, and it's starting to all come together."
Masters champion Bubba Watson, Chris Kirk and Paul Casey each had 66 while playing in calmer and slightly softer morning conditions. Keegan Bradley was at 67, notable not because it was his best score at Muirfield Village but because it was his first time in his four years on the PGA Tour that he did not use a belly putter.
Adam Scott, who won at Colonial Sunday in his debut at No. 1 in the world, lost momentum with a shot into the water for double bogey on No. 9 and settled for 69.
Phil Mickelson also looked sharp, at least for 15 holes. He was 5 under after the 15th hole, one shot off the lead at the time. But he hit into the water on the par-3 16th and did well to escape with bogey. He then double bogeyed Nos. 17 and 18 for 72. "Just threw away a good round," he said.
McIlroy's only scare came on No. 7 when his spikes caught and applied a little more torque on his knee. He said he had never experienced that before, though he felt some ice and work in the fitness trailer should take care of it.
"The inside of it is sore, a little swollen," McIlroy said. "Some treatment and I should be fine for the morning."