Adam Scott warmed up for the defence of his Masters title in stunning fashion with a course record-equalling 62 in the first round of the Arnold Palmer Invitational on Thursday.

Scott carded two eagles, seven birdies and one bogey at Bay Hill to claim the lead on 10 under par, matching the course record shared by Andy Bean (1981) and fellow Australian Greg Norman (1984).

"Obviously I'm really thrilled with the start," said world number two Scott, who is closing in on Tiger Woods at the top of the rankings. "It's maybe a little surprising. I don't know where it came from, but the putter certainly got hot."

Scott is making his first appearance at Bay Hill since 2009. He missed the cut in his last two starts and his only top-10 finish in six previous appearances came in 2004, when he tied for third.

"I just had a few frustrating years here and left it off the schedule," Scott told reporters after his round. "Coming back fresh was obviously a good thing. But I like the changes they've made since the time I have not been here and today was just one of those days where the hole was a bit like a bucket."

Scott revealed he had been suffering from flu-like symptoms for the past two days, but felt that might have been a positive rather than a negative.

"I went out there just trying to get the ball around," he added. "I've played a lot like this and sometimes it works in your favour because you have lower expectations."

Scott cannot overhaul the absent Woods - the defending champion pulled out on Tuesday with ongoing back problems - in the rankings with a victory on Sunday, but would claim top spot before the year's first major if both players did not compete again ahead of Augusta.

Scott started on the 10th and birdied his opening hole before picking up another shot on the par-five 12th after getting up and down from a greenside bunker.

He then holed from 25ft on the 14th and from a similar distance off the green on the next, before continuing his hot putting steak by making an eagle from 35ft on the par-five 16th.

The solitary bogey came from an errant approach to the 18th, but the 33-year-old bounced back quickly with a birdie from close range on the third and another eagle from 20ft on the fourth.

Further birdies on the sixth and seventh meant matching front and back nines of 31 and left Scott three ahead of Japan's Ryo Ishikawa and American John Merrick, with Spain's Gonzalo Fernandez-Castano, who also covered the back nine in 31, on six under.

England's Paul Casey and Welshman Jamie Donaldson were a shot further back on five under, with Ian Poulter and Graeme McDowell four under and European number one Henrik Stenson three under.

US Open champion Justin Rose and WGC-Cadillac Championship winner Patrick Reed, playing alongside Scott, shot 71 and 69 respectively, but Scott's predecessor as Masters champion, Bubba Watson, withdrew after an opening 83 - which contained an 11 on the par-five sixth - citing allergy problems.

English amateur Matthew Fitzpatrick returned a highly creditable 71, the 19-year-old from Sheffield carding three birdies and two bogeys.

"I felt quite composed, I didn't get down or get too upbeat," said Fitzpatrick, who claimed the silver medal as leading amateur in the Open Championship at Muirfield last year and then won the US Amateur title at Brookline.

That victory means Fitzpatrick has exemptions into three of the four majors in 2014 - the Masters, US Open and Open - as long as he remains an amateur. In January, he withdrew from Northwestern University to pursue a full-time amateur golf career.