That saw McIlroy, who held a one-shot lead at the end of the opening day, maintain his advantage, with Zimbabwe’s Brendon de Jonge the nearest challenger on 10 under, two clear of Russell Henley.

Behind Henley were two Britons on seven under, England’s Lee Westwood and Russell Knox of Scotland, with Welshman Jamie Donaldson one of three men on six under.

McIlroy was struggling for form this time last year and hit a real low point at Palm Beach when he withdrew midway through his second round complaining of fatigue.

“It’s a different end of the spectrum I guess,” McIlroy told pgatour.com. “I wasn’t quite comfortable with my golf swing. I was still tinkering with equipment. I just wasn’t feeling in control of, you know, what I needed to be in control of.

“This year is obviously a lot different.”

McIlroy put his improved form in Florida this time around down to regaining his confidence.

“When you hit a few good shots, your confidence can go up quite quickly but then you hit one bad one, it can sort of go down again and that’s where I was sort of most of last year,” he said.

“Now I feel I’m happy with where my swing is, and even if I do hit a loose shot, I can get over it much quicker and much easier because I have the confidence in what I’m doing.”

De Jonge, who carded eight birdies in his six-under 64, could have been level with McIlroy but for a bogey on his final hole, the par-four ninth.

Knox was blemish-free as he sunk seven birdies in his 63, which matched the best of the day, while Westwood carded six birdies against a single bogey for a 65.

Luke Donald kept up a good day for the British contingent as he moved into a share of ninth on five under with a 68, while further down the leaderboard compatriot Paul Casey just made the cut at level par, as did Tiger Woods and Sergio Garcia.

Among those falling just the wrong side of the line were Phil Mickeson and Angel Cabrera, with Padraig Harrington, David Lynn, Darren Clarke and 2013 champion Michael Thompson also among those who missed out.