Rory McIlroy found high-altitude golf to his liking as he opened the WGC-Mexico Championship with a sublime 63 to earn the outright lead on day one.
McIlroy's all-round game was in excellent order throughout, bar one blemish at the par-five sixth, as he hit 17 of 18 greens in regulation and backed up his precise approach play with some assured putting, his longest successful putt of 20 feet indicating just how strong his iron-play was.
Dustin Johnson, the champion in Mexico two years ago, began his round with three consecutive birdies and went on to fire a bogey-free 64, while last year's runner-up, Justin Thomas, is alongside Matt Kuchar on five under par.
Tiger Woods tugged his opening tee-shot out-of-bounds and had to dig deep to salvage a level-par 71, while defending champion Phil Mickelson appeared to be feeling the effects of playing four weeks in a row as he slumped to a 79 which left him tied for 70th, with only Sanghyun Park below him on the leaderboard.
But the first day belonged to McIlroy, who held the 36-hole lead at Club de Golf Chapultepec in 2017, and he gave himself two early confidence boosters on the greens when he holed birdie putts of 12 feet and eight feet on the 11th and 12th.
He took advantage of the long 15th and clipped a delightful wedge to two feet at 17 to set up another birdie before producing the shot of the round at the 305-yard first, where his towering fade with a two-iron pitched softly on the front of the green and rolled inches left of the cup before coming to rest six feet from the pin.
McIlroy's putting was again perfect as he rattled in the eagle chance, and he picked up further shots from inside five feet at two of the next three holes before suffering his only setback of the day at the sixth, where he pulled his drive into the trees and his initial attempt to get his ball back into play was scuppered by a branch.
He did well to limit the damage to a six, and he clawed the dropped shot back with an excellent putt from 20 feet at the eighth before a rock-solid par at nine capped his second 63 in seven days.
Johnson also started at the 10th and looked in cruise control as he followed his opening salvo of birdies with three in four holes from the 17th, although he managed only one more thanks to a 25-foot putt on the fifth.
The world No 3 parred safely in to remain on seven under and two clear of Kuchar and Thomas, who drove the green at the 412-yard 12th only to walk off with a three-putt par, although he then atoned with an impressive pitch-in for eagle at the long 15th.
Three birdies over the front nine added up to a 66 which was later matched by Kuchar, who put his recent caddie controversy behind him to put himself in the running for a third victory of the wrap-around season.
Tyrrell Hatton, was denied a place in last year's Mickelson-Thomas play-off by an unfortunate pitch-mark 12 months ago, enjoyed a run of four birdies in six holes in a 67 which left him one ahead of Ryder Cup team-mate Ian Poulter, who mixed six birdies with three bogeys in his 68.
Sergio Garcia cantered to five under before his round derailed with a double-bogey at the fifth and another blemish at the eighth as the Spaniard settled for a 69, while Woods will look for a fast start to his second round early on Friday after a disappointing first knock in Mexico.
Woods was perhaps distracted by a lengthy and unorthodox introduction on the first tee, and he had little time to regain his composure before his pulled fairway-wood kicked over the out-of-bounds fence, and his second effort was perilously close to finding the same result.
He eventually did well to get up-and-down from a greenside bunker to limit the damage to a six, but he then looked more like the Woods of old when he reeled off three straight birdies from the fourth, only to give one shot back at the tough eighth.
Woods slipped over the card again when he three-putted the 13th green, but his fourth birdie of the day at the 15th restored parity, and he at least managed to get round in eight fewer shots than long-time rival Mickelson.
The veteran left-hander bogeyed three of his first four holes, and his fatigue was evident over the last third of his round as he carded four further bogeys and a double-bogey five at the short seventh, where he found water from the tee, and a par at the ninth merely ensured he avoided the indignity of failing to break 80.