Adam Scott

Dustin Johnson responds to late challenge to win the WGC Mexico Championship

Dustin Johnson responds to late challenge to win the WGC Mexico Championship

Dustin Johnson didn't flinch when a challenge arrived out of nowhere Sunday, playing mistake-free over the final five holes to win the WGC Mexico Championship in his debut as the No. 1 player in the world.

Johnson's four-shot lead going to the back nine turned into a one-shot deficit when Spanish rookie Jon Rahm ran off an eagle and two birdies at Chapultepec Golf Club. Johnson caught him with a birdie on the par-five 15th, and closed with three solid pars for a three-under-par 68.

Rahm had gone 59 holes without a three-putt until taking two in a row at the worst time to fall back.

Johnson's last test was from a fairway bunker on the 18th, and he blasted that out to...

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