Rory McIlroy took pole position at the WGC-Mexico Championship after an impressive opening round.

The Northern Irishman hit 17 of 18 greens to get round Club de Golf Chapultepec in 63 – eight under par and his level-best for the season.

His near-spotless round put him a shot ahead of Dustin Johnson in second and three ahead of Justin Thomas and Matt Kuchar, who are tied for third.

The former world number one, whose last PGA title was at the Arnold Palmer Invitational in March, suggested victory at the WGC would be a happy by-product of his current focus on the fundamentals.

"Practising the right way, thinking well, training well, eating well, all the stuff that I try to do," he said in comments published by the Golf Channel.

"Winning is a by-product of doing all the little things well and I feel like I'm on a really good journey of doing that. I think it's just a matter of time.

"I can't put pressure on myself, I can't push it. I'm off to a great start this week but I literally have taken each and every day this year one day at a time and that's the way I'm going to treat it. Not just this week, but going forward."

Setting off down the back nine, two-time WGC winner McIlroy picked up shots on the 11th, 12th, 15th and 17th.

He nearly pulled off a remarkable feat after the turn, coming close to acing the 305-yard first hole with a two iron.

Picking up an eagle, he notched up more birdies on the second and fourth and, after dropping a shot on the par-five sixth, he hit another birdie on the eighth and parred the ninth.

It was an encouraging performance for McIlroy, who announced on Thursday that he will miss the Irish Open to focus on preparing for the Open Championship at Royal Portrush.

It was also a decent day for Englishman Tyrell Hatton, whose 67 put him just behind the chasing pack of Johnson, Thomas and Kuchar.

Tied for fifth with South African George Coetzee, Hatton is a shot ahead of fellow Englishman Ian Poulter, who sits in seventh with Billy Horschel, Kiradech Aphibarnrat and David Lipsky.

Tiger Woods, who has 18 WGC wins under his belt, hit par to sit tied for 25th with England's Paul Casey and eight others.

And it was a wholly disappointing day for last year's champion Phil Mickelson, who went eight over par to finish a shot off the bottom tied 70th.