Paul Casey expected to be chasing someone Friday in the Memorial, figuring it would be Rory McIlroy.
After two holes, Casey had the lead to himself at Muirfield Village in Dublin, Ohio, and that was only the start of another big day. He took advantage of the par 5s for another 6-under 66, giving him a three-shot lead over Masters champion Bubba Watson going into the weekend.
McIlroy, whose 63 was the lowest first round in the 39-year history of the tournament, was barely in the picture. He struggled to a 78, courtesy of three straight double bogeys (Nos. 13-15) and his fourth consecutive PGA Tour event with a nine-hole score of 40 or higher. McIlroy went from a three-shot lead to nine shots behind.
"It seemed like anything that could sort of go wrong did go wrong out there," said McIlroy, who didn't blame a sore left knee as much as his inability to hit fairways. "Take those three holes out of it, then it wouldn't actually have been that bad a day."
Casey, taking another step on a long road back from injuries, was at 12-under 132.
He made his first birdie with his best drive of the day on the par-5 11th, setting up a 4-iron onto the green for a two-putt birdie. He made eagle on the par-5 15th for the second straight day, and he stuffed it close around the turn for birdies to start pulling away from the field.
"To be honest, I thought I was going to be playing a round to try and maybe catch a couple of guys," Casey said. "I woke up checking the scores to see what Rory was going to be. That's really what I was going to be doing -- see how many under I was going to have to try to shoot to chase. Obviously, that didn't happen."
Watson's round featured six birdies, five bogeys and an eagle. And a bogey-bogey finish wasn't enough to ruin his day.
"I can't look at the bogeys," Watson said. "I've got to look at where I'm at. If you told me it's my best two days around this golf course, I'd take it."
Chris Kirk (70) was four shots behind. Hideki Matsuyama (67) and Martin Flores (68) were five back.
Adam Scott, who won the Colonial in his debut at No. 1 in the world, shot 70 and was at 5-under 139.
Phil Mickelson shot a 70 and was 10 strokes back.
McIlroy shot a 43 on the back nine -- he began the round at No. 10. He twice hit the trees on the 13th hole and made double bogey. He hit into the water on the 14th for double bogey. And then he double-hit a wedge on the 15th to make it three straight double bogeys.
"Going into the weekend, not exactly where I want to be. But it could be worse," said McIlroy, who won the BMW PGA Championship in England on Sunday.
LPGA: Jennifer Johnson tied the course record with a 9-under 62 to take the ShopRite Classic lead in Galloway Township, New Jersey.
The 22-year-old, the winner last year in Mobile, Alabama, had 10 birdies -- five straight on Nos. 9-13 -- and a bogey at Stockton Seaview Hotel & Golf Club.
Haru Nomura shot a 63, and San Jose's Christina Kim opened with a 64. Kim finished with seven birdies, including a 35-foot putt on No. 11 that she called "one of the longest putts I've made since the '90s."
Top-ranked Inbee Park shot a 66, while No. 2 Stacy Lewis and Michelle Wie had 67s. Teenager Lydia Ko was at 68.
Champions: Mark Calcavecchia and Wes Short Jr. shot 6-under 66s to share the Principal Charity Classic lead in Des Moines, Iowa. Short birdied No. 18 to join Calcavecchia atop the leader board at Wakonda Club. Bobby Clampett, Peter Senior and Shane Lowery were at 67.
European: Alvaro Quiros shot a 5-under 67 in the Nordea Masters for a share of the lead with Victor Dubuisson (69) and Eddie Pepperell (72). They were at 6-under 139 on PGA Sweden National in Malmo. Second-ranked Henrik Stenson topped the group at 5 under after a second-round 70.