Scott Stallings shot his best round of the year, a six-under-par 66, to lead by one stroke at the end of the first day of the Memorial Tournament at Muirfield Village.
The 27-year-old has battled injury this season and had not carded a round under 70 since January, but on Thursday he carded six birdies and an eagle against two bogeys to lead by one from fellow Americans Spencer Levin and Erik Compton. A further two strokes back was a group of seven players on three under.
"We've got a long way to go," Stallings told www.pgatour.com. "I was happy to get a good round under par. I haven't had a round under par since Saturday at Augusta. It's been a long time.
"[I've] been really struggling with my game coming back from injury, and I was healed, I wasn't healed, and kind of the ebbs and flows that go along with that. It's been interesting to say the least."
Rory McIlroy recovered from a nightmare quadruple-bogey seven on the ninth hole to climb back to put himself in the top 20 on one under. The Northern Irishman went into the tournament after missing two successive cuts for the first time in his career and handing back his world number one ranking to Luke Donald.
And for a time things looked set to go from bad to worse. McIlroy found two bunkers and the water once at the ninth, but produced a sterling recovery with two birdies and a fifth hole eagle for a final total for the round of 71, the same as Donald.
Like McIlroy, Tiger Woods showed signs of a recovery from his recent travails as he posted a two-under-par round of 70, tarnished only by a double-bogey at the par-four 18th hole.
Woods is looking for his fifth title at the Memorial but went to Ohio with few signs of form after finishing below 40th in each of his last three tournaments since winning the Arnold Palmer Invitational at Bay Hill.
Ernie Els was two under and Rickie Fowler one under, while Vijay Singh and Jim Furyk were among those finishing for the day on level par, as was England's Greg Owen.
Brian Dabis and Justin Rose were one over.