The power games of both McIlroy and Johnson enabled them to separate themselves from the field on the high altitude Golf Club De Chapultepec layout in Mexico City.
Johnson’s 64 was two better than countrymen Justin Thomas and Matt Kuchar who share third at 5 under, while England’s Tyrrell Hatton and South African George Coetzee are equal fifth at 4 under.
After beginning his round on the 10th, McIlroy was rock solid with a 4 under opening nine and caught fire after the turn.
At the downhill reachable par-4 first, he needed only his driving iron and almost made an albatross with his tee shot nestling about 6 feet beyond the pin.
He converted the putt for eagle before another birdie at the second and then at the fourth to reach 8 under.
2-iron.February 21, 2019
A bogey 6 on the par-5 6th hole quelled McIlroy’s momentum only briefly as he added his final birdie of the day at the par-4 8th.
Johnson used brute force at times on the narrow tree-lined Chapultepec course, capitalising on the extra distances high above sea level, driving the green on the 383-yard second hole which led to one of 7 birdies in a bogey-free round of golf.
Queenslander Cameron Smith led the Australian contingent with a 2 under round of 69, one better than former amateur teammate Jake McLeod who shares 19th place after an opening 70 and is in the elite field courtesy of finishing first on last year's PGA Tour of Australasia Order of Merit.
After his breakthrough win at last week's World Super 6 Perth, New Zealander Ryan Fox is T35 after a 72, ACT golfer Matt Millar began with 74 and Marc Leishman is ahead of only 3 people in the 72-man field after struggling to a 77.
Among the other notables, Tiger Woods opened with an even par 71, Jordan Spieth 75 and defending champion Phil Mickelson is second last after a 79.
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