On an extremely windy afternoon at Austin Country Club with gusts of up to 35 miles per hour (56 kph), Johnson coped manfully with the elements to beat German Martin Kaymer 3&2 .
"Putting is the hardest part," Johnson told Golf Channel after improving to 2-0-0 overall with his second straight win over a major champion. "It’s very breezy and then really gusty at times."
Despite two wins from two matches, Johnson was not guaranteed of advancing out of the group stage. He must win or halve his Friday match against compatriot Jimmy Walker to be certain of advancing to the final 16.
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The format divides the 64 players into 16 four-man groups, with the winner of each group entering the knockout stage on Saturday.
After losing to Dane Soren Kjeldsen on Wednesday, McIlroy got a win on Thursday when his scheduled opponent Gary Woodland withdrew, citing personal family reasons.
Even with that walkover, however, McIlroy still needed Kjeldsen to lose his second match to have any chance of advancing out of the round-robin group stage.
But Kjeldsen duly shut the door on the Northern Irishman, beating Argentine Emiliano Grillo 4&3 on Thursday to improve to 2-0-0.

Rory McIlroy of Northern Ireland plays against Soren Kjeldsen of Denmark during the first round of the World Golf Classic - Dell Match Play golf tournament at Austin Country Club.

Image credit: Reuters

Kjeldsen said he relished the tough conditions.
“I’m brought up in this," he said. "The way I play golf, I like to shape shots, like to change the trajectory. When I saw it being windy today I was really happy.”
Swede Alexander Noren is also guaranteed of being part of the sweet 16, after beating Austrian Bernd Wiesberger 3&2.
McIlroy was not the only highly-ranked player eliminated from the final 16 with world number four Hideki Matsuyama also making an early exit after losing to Englishman Ross Fisher 2&1.
The wind caused all sorts of problems and a watery grave for many a ball, even a shank by American Charles Howell, who had no problem assigning the blame to the conditions.
“(It was) difficult enough to cause a shank,” he said after escaping with a 1-up win over Spaniard Rafa Cabrera-Bello.
Phil Mickelson, who improved to 2-0-0 thanks to a 5&4 thumping of fellow American Daniel Berger, said it was fortunate that the match play format was being used rather than stroke play, given the conditions.
"Given the severity of the greens and so forth, certainly there are holes we're going to look ridiculous on," he said after chipping clean across a green into a water hazard.
"I think it's fun and it's great for match play because you don't worry about the stroke. It's just relative to your opponent."
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