Miami - World number three Jason Day of Australia fired a six-under par 66 Thursday to grab a one-stroke lead after the first round of the US PGA Arnold Palmer Invitational.
The 28-year-old bounced back twice after stumbles to top the leader board at Bay Hill in Orlando, Florida, and dropped a tense 10-foot par putt at 18 to finish on top.
"It was kind of one of those days where everything went well," Day said. "If you are driving it well you can give yourself some opportunities on the green. I drove it pretty well. I drove it on a string."
Day, who won his first major title at last year's PGA Championship, led a pack that included compatriots Adam Scott, who is seeking his third win in as many starts and Marc Leishman, plus Sweden's Henrik Stenson and Americans Troy Merritt and Brendan Steele.
England's eighth-ranked Justin Rose, who holed out for an eagle from 112 yards at the third and sank a 20-foot putt for another eagle at 16, was in a pack of 10 sharing seventh on 68.
"I hit a nice wedge from 112 yards," Rose said. "Those are always a bonus."
Day made bogey at the par-3 second but bounced back with birdies on four of the next six holes, capping the run with a 31-foot birdie putt at the eighth.
But Day took a double bogey to finish the front nine, going out of bounds left off the tee and taking five shots just to reach the green.
"That was the only one that was weird about the day. That one came out of the blue," Day said of his tee shot. "Unfortunately, it's not always A-grade stuff. When things pop up you have to understand it's just one bad swing and try and fight on the back side."
Day answered again with three birdies in four holes, sinking short putts at the par-5 12th and par-4 13th and dropping an 18-footer at the 15th.
A 10-foot eagle putt at the par-5 16th put Day into the lead at 6-under and he sank a tense nine-foot par putt at 18 to rescue par from greenside rough to finish on top.
"I played the par-5s 5-under," Day said. "You have to capitalize on the par-5s here."
Day's round was the lowest at Bay Hill with a double bogey since Canada's Stephen Ames shot 65 in 2004 - a good omen with the year's first major at the Masters only three weeks away and Day having already finished second at Augusta National in 2011 and third in 2013.
Sixth-ranked Scott, the 2013 Masters champion, sank three par putts from beyond five feet, another from 10 feet and yet another from 12 feet.
"There was some scrambling going on," Scott said. "I wasn't really sharp but I got away with it. I managed myself well and made some good putts and kept whatever momentum I had going and got off to a good score."
Scott, coming off titles at the Honda Classic and the World Golf Championships event at Doral two weeks ago, was pleased with his start.
"I didn't play my best golf tee to green but I chipped and putted really well," he said. "We got good conditions. The course is perfect. I had to take advantage of that."
Lucas Glover, the 2009 US Open champion who began on the back nine, was atop the leader board at six-under with three holes remaining. But the 36-year-old American, who has not won since 2011 at Quail Hollow, found a bunker at the par-3 seventh and took a double bogey, falling into the pack on 68.
Leading scores after the first round of the US PGA Arnold Palmer Invitational at Bay Hill in Orlando, Florida, (USA unless noted, par 72, a- amateur):
66 - Jason Day (AUS)
67 - Marc Leishman (AUS), Brendan Steele, Adam Scott (AUS), Henrik Stenson (SWE), Troy Merritt
68 - Francesco Molinari (ITA), Chris Kirk, Justin Rose (ENG), Emiliano Grillo (ARG), Kevin Chappell, Cameron Tringale, Lucas Glover, KJ Choi (KOR), Paul Casey (ENG), Jamie Lovemark
69 - William McGirt, Adam Hadwin (CAN), Martin Laird (SCO), Smylie Kaufman, Freddie Jacobson (SWE), Chris Wood (ENG), Billy Hurley, Keegan Bradley, Brian Harman, Maverick McNealey-a