DUBLIN, Ohio, May 31, 2012 (AFP) - Stallings birdied three of the last four holes to stand on six-under par 66 after 18 holes, one stroke ahead of fellow Americans Spencer Levin and Erik Compton and three clear of the rest of the star-studded field.
At the Muirfield Village layout designed by Jack Nicklaus, Woods shared 11th on 70 with a group that included Australian Adam Scott and three-time major winner Ernie Els.
"It certainly could have been a lot lower, but I'm pleased with the way I hit the golf ball," Woods said. "I didn't do anything great and I didn't do anything poorly. It was just a solid round."
World No. 1 Donald of England and McIlroy, the Northern Ireland prodigy who will defend his US Open title in two weeks at The Olympic Course in San Francisco, were another stroke adrift in a group on 71.
"It wasn't the start that I wanted to get off to, being 4-over through three holes," McIlroy said. "But I hung in there well and proud of myself for the way I just fought back. To finish the round under par was a really good effort."
Stallings answered a bogey at the second with birdies at the par-3 fourth and par-5 fifth plus an eagle at the par-5 seventh.
After a birdie at the par-5 11th and a bogey at the par-3 12th, Stallings birdied the par-5 15th, par-3 16th and par-4 18th to surge to the top of the leaderboard.
"I was happy to get a good round under par," Stallings said. "I haven't had a round under par since Saturday at Augusta. It has been a long time. Been really struggling with my game. It has been interesting to say the least.
"I'll go out tomorrow and try to do the same. We've got a long way to go."
That fact eases the worries for Woods, the 14-time major champion whose victory in March at Bay Hill snapped a 17-month win drought.
"I didn't do anything poorly. I was just very consistent," Woods said. "Over the next three days, hopefully I can play as well as I did today."
Woods, who began on the 10th tee, birdied the 15th and 17th before taking a double bogey at the 18th. He bounced back with birdies on the front nine's two par-5 holes but the damage was done.
"I haven't played the par-5s particularly well the last few tournaments," Woods said. "I feel very pleased with the way I hit the golf ball all day and it was nice to actually play the par-5s under par for a change."
McIlroy, who also began on the back nine, went from bunker to water with an awkward stance at the par-3 12th on his way to a quadruple bogey 7 and even after pulling back strokes with birdies at 14 and 15 gave one back with a bogey at the 17th.
A birdie at the par-4 third, an eagle at the par-5 fifth and a closing birdie at the ninth brightened McIlroy's day somewhat.
"I just tried to stay patient and not even think about the score, just think about what I'm working on in my swing and try and make good swings," McIlroy said. "That's really all I could do. There was a little bit of encouragement and to string a few good holes together on the back nine was nice."
Donald, another back-nine starter, opened with a bogey and closed his first nine with a double bogey. Birdies at the third and par-5 seventh left the Englishman under par but somewhat unhappy.
"Hopefully that's my loose round out of the way," Donald said. "I didn't hit the ball well. I was scrambling a lot. But fortunately I putted pretty well and I'm pretty happy with the score in the end. It wasn't that solid of a round tee to green. I'm going to need to tidy that up."
Els had two birdies and a bogey on back the front and back nines.
"Good start," Els said. "You've got to have a little bit of game here. It tests your whole game and the greens are unbelievable. The greens are as pure as you're ever going to find. So it's really a pleasure to play here."
Phil Mickelson fired a 79 and withdrew, saying he was tired and needed rest before playing the US Open in two weeks, attributing his troubles to playing three weeks in a row and then going to France and Italy to celebrate his wife Amy's 40th birthday.
"I'm hitting it so poorly," Mickelson said. "I have to look at what's best for me to play in the US Open and I'm going to take the next few days to kind of rest up."
Scores on Thursday after the first round of the $6.2 million US PGA Memorial tournament (USA unless noted, par 72):
66 - Scott Stallings
67 - Spencer Levin, Erik Compton
69 - Blake Adams, Andres Romero (ARG), Aaron Baddeley (AUS), Rory Sabbatini (RSA), Brandt Snedeker, Matt Every, Daniel Summerhays
70 - Bud Cauley, Mark Wilson, Tiger Woods, David Hearn (CAN), Ryan Moore, Adam Scott (AUS), Scott Piercy, Ben Curtis, Ernie Els (RSA)
71 - Greg Chalmers (AUS), Trevor Immelman (RSA), Luke Donald (GBR), Rory McIlroy (NIR), Robert Garrigus, Charlie Wi (KOR), David Mathis, Kyle Reifers, Dustin Johnson, Geoff Ogilvy (AUS), Rickie Fowler, John Huh, Jonathan Byrd, Harris English, Stewart Cink
WD - Phil Mickelson, Tom Gillis, Boo Weekley, Bae Sang-Moon (KOR)