|WGC-Mexico Championship first-round leaderboard|
|-8 R McIlroy (NI); -7 D Johnson (US); -5 J Thomas (US), M Kuchar (US); -4 T Hatton (Eng), G Coetzee (SA)|
|Selected others: -3 I Poulter (Eng); -2 S Garcia (Spa); -1 A Rai (Eng), T Fleetwood (Eng); level D Willett (Eng), T Woods (US); +1 R Knox (Sco), +2 L Westwood (Eng); +4 J Spieth (US); +8 P Mickelson (US)|
Northern Ireland's Rory McIlroy carded an eight-under 63 to take a one-shot lead after the opening round of the WGC-Mexico Championship.
The 29-year-old world number eight began his round at the 10th and posted seven birdies and an eagle.
American Dustin Johnson, winner in 2017, is second after a bogey-free 64.
Englishman Tyrrell Hatton compiled four birdies on the back nine in a 67 but defending champion Phil Mickelson had eight bogeys and a double in a 79.
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McIlroy, who won the last of his 14 PGA Tour titles at the Arnold Palmer Invitational in March last year, eagled his 10th after sending a two-iron tee shot to five feet at the 305-yard par four.
He was two clear after pitching to three feet from 123 yards at his 13th before dropping his only shot of the round at his 15th after both his drive and second were affected by trees down the left.
"It felt pretty stress-free but I wouldn't say it was easy," said the four-time major champion.
"I hit a lot of good shots, I left myself a lot of tap-ins for birdies and had a nice eagle on the first hole as well.
"If I'm excited about anything in my game, it's the way I've putted the last few weeks.
"Also my attitude. I'm not putting myself under any pressure, I've got things in a really nice perspective. I think that's probably 80% of the reason why I'm playing good golf over the first few weeks of the year.
"I saw some really good signs last year. I played myself into final groups and had some good chances to win and I think this year is just building upon the good stuff I was able to do last year."
Ian Poulter returned six birdies in a 68, while fellow Englishman Tommy Fleetwood, runner-up to Johnson two years ago, dropped two shots in his final three holes in a 70.
Tiger Woods, winner of 18 WGC titles from 1999-2013, sent his opening tee shot out of bounds at Chapultepec and ran up a double bogey, but the 43-year-old made three successive birdies en route to a level par 71.