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...