Rory McIlroy brilliantly capitalised on a stroke of good luck to make a superb start to his bid for a second victory in the Arnold Palmer Invitational.

McIlroy, who won at Bay Hill in 2018 and has finished no worse than tied sixth in each of the last four years, fired seven birdies – including five in a row on his back nine – and one bogey in an opening 66 to set the early clubhouse target.

At six under par McIlroy led by one from US Open champion Bryson DeChambeau, with Jason Kokrak on four under and Scotland's Martin Laird, the 2011 champion, another stroke back alongside France's Victor Perez.

Playing alongside McIlroy, defending champion Tyrrell Hatton and 2019 winner Francesco Molinari both struggled badly, Hatton returning a five-over-par 77 and former Open champion Molinari shooting 78.

Starting from the 10th, McIlroy picked up shots on the 14th and 17th before making a mess of the 18th from the middle of the fairway and showing his frustration by slamming his club into the turf following a clumsy chip from short of the green.

A somewhat sheepish smile was back on McIlroy's face after he holed from 55 feet on the second, the putt having been struck much too hard but hitting the pin and dropping for an unlikely birdie.

There was nothing fortunate about the curling birdie putt McIlroy holed from 20 feet on the third, nor the two putts from long range for another on the par-five fourth.

And after a superb approach to the fifth set up another birdie, McIlroy soon made it five in a row by finding the green on the par-five sixth in two and two-putting from 25 feet.

Hatton had opened with four straight pars before dropping shots on the 14th and 15th after failing to get up and down from greenside bunkers on both holes.

The world number six, who is the top-ranked player in the field, then three-putted the par-five 16th from long range for a disappointing par and threw his ball into the water after a bogey on the 18th.

Hatton also carded a hat-trick of bogeys from the second before carding his only birdie of the day on the par-five sixth.