MEMPHIS, Tennessee, June 7, 2012 (AFP) - The American duo had a one-stroke lead over Atwal, Americans J.J. Henry and Jeff Overton and South Korean Noh Seung-Yul with McIlroy, Ireland's Padraig Harrington and Australian Robert Allenby among those two strokes adrift on 68.
A week before the start of his US Open title defense, Northern Ireland's McIlroy began off the 10th tee, birdied the par-4 12th and par-3 14th and birdied the first and sixth holes only to suffer bogeys on three and eight.
"I felt like that was about the best round of golf I played in a while," McIlroy said. "It could have been a lot better. The scoring doesn't look too good. Off to a decent start, definitely so. Lot of good signs out there."
World number two McIlroy will play alongside English pair Luke Donald, the world number one, and third-ranked Lee Westwood in the first round of the US Open at The Olympic Club next Thursday.
Atwal opened with back-to-back birdies and birdied the fifth before a bogey at the seventh. He birdied again at 15 only to take a bogey at the 17th and closed with another birdie to pull within a stroke of the leaders.
"I've been struggling all year, so not bad," Atwal said. "I've actually started to hit it a little better the last few weeks, just building on that. It's a good score to have on this golf course."
And Atwal did it without playing a practice round because he tried in vain to qualify for the US Open early in the week.
Noh birdied two of his first three holes after starting on the back nine then birdied three in a row after the turn to put himself one off the lead.
Harrington, also a 10th tee starter, birdied the 12th and the TPC Southwind's two par-5 holes, the 16th and third, before a bogey at the par-3 fourth dropped him back to 68.
"I thought the scoring would be a little bit better. I'm trying to figure out why it wasn't," Harrington said. "It was windy from early on. I got distracted a number of times with the wind.
"There's room for improvement the next couple of days."
Merrick, who also did not play a practice round, birdied three of the first four holes before taking a bogey at the seventh, added back-to-back birdies on the 12th and 13th holes and another at the 16th before closing with a bogey.
"It was nice to get off to a decent start," Merrick said. "Had a loose shot there on 18, but you can't hit every shot perfect out there. So I was really happy."
But he is not looking ahead too far, even though he sits atop the leaderboard.
"You don't start thinking about leading or winning the tournament until back-nine on Sunday," Merrick said. "You're just trying to do the best you can Thursday, Friday, and Saturday. You don't want to think about winning until the last hole or last shot. You're a long ways from thinking about winning."
Maggert, the 2006 St. Jude winner, began on the back nine and birdied the 12th, ran off three birdies in a row starting at the par-3 14th and eagled the third to seize command before bogeys at the fifth and eighth.
Maggert underwent shoulder surgery last June but has recovered to 100 percent as he enjoys a 22nd PGA season.
Leading scores on Thursday after the first round of the $5.6 million St. Jude Classic (USA unless noted):
66 - Jeff Maggert, John Merrick
67 - Arjun Atwal (IND), Jeff Overton, J.J. Henry, Noh Seung-Yul (KOR), Troy Kelly
68 - Robert Allenby (AUS), Rory McIlroy (NIR), Padraig Harrington (IRL), Ken Duke, Chad Campbell, Davis Love, Yang Yong-Eun (KOR), John Daly, Lee Janzen, J.J. Killeen
69 - Kevin Stadler, Bryce Molder, Fredrik Jacobson (SWE), Tim Clark (RSA), Kevin Kisner, Luke Guthrie, Skip Kendall, Charles Howell, Paul Stankowski, Danny Lee (NZL)