By Mark Lamport-Stokes
DUBLIN, Ohio (Reuters) - American journeyman Chris Riley made a mockery of his poor record at the Memorial tournament by charging into an early one-shot lead in Thursday's opening round.
On a sun-splashed day at Muirfield Village Golf Club where Riley has missed the cut in his three previous starts, the 37-year-old fired a sizzling six-under-par 66.
He recorded eight birdies and two bogeys on the undulating, heavily wooded layout to upstage some of the biggest names in the game.
Chris DiMarco birdied five of his last eight holes for a 67 to lie one shot off the pace with fellow American Josh Teater.
British world number one Luke Donald recovered from an opening nine of two-over 38 to card a six-birdie 70 while fourth-ranked American Phil Mickelson returned a 72.
But Riley, who claimed his only PGA Tour victory at the Reno-Tahoe Open in 2002, took the greatest advantage of a relatively calm morning in the event hosted by Jack Nicklaus to soar to the top of the leaderboard.
"I really putted good," the slender American told reporters after totaling only 25 putts. "I made a lot of nice par saves.
"I made one on six, my 15th hole, from like 20 feet for par and on the first hole I made about a 15-footer for par.
"It was just one of those days where everything was going in the hole, and it felt pretty good to see that."
Riley was delighted to be back in the field at Memorial, having not played here since 2002.
"It was very unexpected," said the American, who qualified for the event in the final exemption category by finishing 90th in last year's PGA Tour money list.
"I didn't even think I had a chance of getting in here this year ... so I was really excited. To be able to come back here is a pretty big deal," added Riley, who had not broken par in his previous six rounds at Muirfield Village.
Donald, who became world number one for the first time with a playoff victory over fellow Briton Lee Westwood in the European Tour's PGA Championship on Sunday, salvaged his round with five late birdies.
His low point came with a double-bogey at the par-four 18th, his ninth hole, where his approach ended up in a bunker and he needed two more shots to reach the green.
"I hit a great eight-iron right at the pin and it came up maybe two yards short of being perfect and kicked back in the middle of the trap," Donald said. "I just got a little bit too cute.
"I hit a poor bunker shot, another poor chip and lipped out the (bogey) putt. So taking four from literally 20 feet wasn't what I was hoping for."
Donald, who played in a high-profile group with Masters champion Charl Schwartzel of South Africa and Mickelson, was warmly greeted by the fans as he made his way round the course.
"A lot of people were saying congrats," he said. "I heard a few 'No. 1' shouts and stuff like that, so you feed off that.
"I'm excited to be there and looking forward to the challenges and excited to hopefully keep playing the way I've been playing."
American world number eight Steve Stricker opened with a 68 to end the first round level with compatriots Rickie Fowler, Rocco Mediate and Matt Betterncourt.
Britain's Justin Rose, who won last year's Memorial tournament by two shots, launched his title defense with an opening 71.
(Editing by Julian Linden)