Australian Marc Leishman trails Sweden's Peter Hanson by one shot after the first round of the US PGA Tour's Byron Nelson Championship.
Hanson fired a five-under-par 65 on Thursday and didn't let his unfamiliarity with the TPC Four Seasons course bother him as he nabbed six birdies with just one bogey.
Leishman, with a four-under 66, is tied second with New Zealand's Tim Wilkinson and American David Duval.
The Australian set the early pace in the Dallas suburb of Irving with what he called a "fairly stress-free" round.
He birdied the par-3 second hole, where his tee shot left him a tap-in from a foot away.
"It was a good surprise," said Leishman, who couldn't see the flight of the ball. "I thought I hit a good shot, but it's hard to tell when you're looking straight into the sun."
He picked up another birdie at the third before his only bogey of the day at the par-4 fourth, which was promptly followed by a birdie at the par-3 fifth.
Two more birdies coming in put Leishman at four-under.
Hanson fired a blistering 30 on the front nine, where he made five of his six birdies, coming home in even-par with a bogey balanced by a birdie at 18.
"Always nice to get off to a fast start," said Hanson, who joined the US Tour full time last season and is seeking his first American win at the $US6.9 million ($A7.5 million) Texas event.
"I got off to a really good start, had a few chances coming back in and made a bit of a clumsy bogey from the fringe on 14, but those things happen," said the Swede, who pulled out of the Wells Fargo Championship at Quail Hollow a fortnight ago with a back injury.
Wilkinson had five birdies included three in a row starting at the fourth, and Duval, who teed off at the 10th, capped his round with three straight birdies from the seventh.
Duval almost pulled out of the tournament because of pain in his right elbow. His decision to play paid off as he twice holed out from the fairway.
"I'm lucky to have had it feel better as the day went on," Duval said of his elbow. "Not 100 per cent by any stretch, but 1000 per cent better than it was."
Germany's Martin Kaymer, winner of the Players Championship on Sunday, headlined a group of eight players on three-under 67. He was joined by South African Tyrone Van Aswegen, fellow German Alex Cejka and Americans Boo Weekley, John Huh, Alex Prugh, Ryan Palmer and Lee Williams.
