Adam Scott left the field trailing in his wake as he closed in on a victory in the Arnold Palmer Invitational in Orlando, Florida which could see him defend his US Masters title as world number one.

Scott held a three-shot lead after a stunning opening 10-under-par 62 at Bay Hill, which equalled the course record held by Andy Bean and his fellow Australian Greg Norman.

And the 33-year-old extended his advantage to seven strokes with a second round of 68, marred only by bogeys on the seventh and 18th, where he three-putted from long range.

Victory on Sunday would leave Scott fractionally behind the absent Tiger Woods in the world rankings, but if neither man played again before Augusta, Scott would assume top spot in the rankings in time for the first major of the year.

Pádraig Harrington is ten shots behind Scott and tied for 16th place after the Dubliner shot 72 to leave himself on four under overall.

Graeme McDowell, however, had a day to forget after following his opening 68 with a second round of 77 that did not feature a single birdie.

After starting from the 10th, McDowell dropped shots at the 13th and 18th to be out in 38 and then finished in nightmare fashion with a double-bogey on the eighth and bogey on the ninth.

McDowell at least made the cut on one over par, while Darren Clarke and England’s Justin Rose made early exits after crashing to second rounds of 78 and 79 respectively.

World number two Scott got off to a slow start on Friday with five straight pars and although he two-putted the par-five sixth for his first birdie of the day, he promptly gave that shot back on the next after failing to get up and down from a greenside bunker.

Another bogey looked possible on the ninth after his drive into the rough left him with an awkward angle to the green, but a superb approach to 10 feet actually set up another birdie.

Scott's birdie attempt on the 10th caught the edge of the hole and span out, but that proved to only be a temporary blip as he holed from four feet on the 11th and five feet on the 12th.

Further birdies on the 16th and 17th took Scott eight clear of the field and a superb drive down the last left him just 150 yards from the pin, but he paid the price for a conservative approach, three putts from 50ft for a bogey dropping him back to 14 under par.

Italy's Francesco Molinari and American duo JB Holmes and Chesson Hadley were Scott's closest challengers on seven under par, with Welshman Jamie Donaldson carding a 71 to lie six under alongside former US PGA champion Keegan Bradley and Brandt Snedeker, while Ian Poulter also returned a 71 to sit at five under.