May 29, 2014 at 7:38p ET
DUBLIN, Ohio (AP) 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 a 9-under 63 and a three-shot lead Thursday after the opening round of the Memorial.
A week ago, McIlroy began his week at Wentworth by announcing he and tennis star Caroline Wozniacki had broken off their engagement. Then, he went out and won the 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.
Masters champion Bubba Watson, Chris Kirk and Paul Casey each had a 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 last week in his debut at No. 1 in the world, lost momentum with a shot into the water for double bogey on No. 9, and he missed some birdie and eagle chances on the back nine that would have allowed him to stay close with McIlroy. He settled for a 69.
Phil Mickelson also looked sharp - at least for 15 holes. He was at 5 under after a birdie on the 15th hole - at the time, just one shot out of the lead. But he hit into the water on the par-3 16th and did well to escape with bogey. He came up short on the 17th and muffed two flops shots on his way to double bogey. And he finished with another double bogey by three-putting the 18th. That gave him a 72.
Stenson had seven birdies and four bogeys on PGA Sweden National's Lakes Course. The Swede is winless this year after sweeping the European Tour's Race to Dubai and PGA Tour's FedEx Cup last season.
Spain's Miguel Angel Jimenez also opened with a 69. He won the Spanish Open two weeks ago at 50 years, 133 days to break his own record as the oldest European Tour champion.