|Final classification of the WGC-Mexico Championship|
|-18 P Reed (United States); -17 B DeChambeau (United States); -15 J Rahm (Spa), E van Rooyen (SA); -14 R McIlroy (NI)|
|Others selected: -13 T Hatton (ing), J Thomas (United States); -11 P Casey (ing); -6 T Fleetwood (ing); -5 L Westwood (Eng); -3 S Lowry (Ire); level D Johnson (United States); 13 G McDowell (NI)|
American Patrick Reed carded a four-67 to win the WGC-Mexico championship at once.
The world number 14, 29, second tied overnight, could afford to bogey the last as he finished 18 cents, one in front of his compatriot Bryson DeChambeau.
World number four Justin Thomas, a front at the start of the last day, slipped to 73 for a sixth.
Jon Rahm’s 67 left him three drifts in third place, with world number one Rory McIlroy a shot further after a 68.
After nine birdies and a hole in one in a course record of 61 on Saturday, Rahm had four of the first five holes to take a header and then managed to save par when his second shot found water at sixth.
On the other hand, Thomas, looking for his 13th PGA title, saw his tee shot fall from a tree into the water in the seventh from par three and he gave up when another shot went to the next after his training finished 80 meters offline.
His ball then ended behind the base of a tree in the 10th, forcing him to play with the lefties, and although he found a way through the trees to return to the fairway, a double bogey resulted.
While other top players fail to capture momentum, DeChambeau, playing in the penultimate group with Rahm and McIlroy, produced seven birdies in nine holes of the sixth to break free from two.
The illustrious Rahm and McIlroy could only play the last nine at par, but Reed, still tenacious, managed two birdies to reduce the gap to one and was tied when DeChambeau left 63 feet in the 17th and 3rd putts.
Despite a low sun causing visibility problems at the Chapultepec Golf Club, Reed designed a two-legged approach for birdies on the 16th and taking the lead.
DeChambeau, who led after two laps, missed a 19-foot birdie chance on the last to finish with a 65 for 17 cents, with Reed clicking in a third successive birdie after a long putt in the 17th.
There was still time for drama when Reed, taking an iron from the tee to the last hole, pushed him right into the trees, but he found green in three and safely two putts for a five to add a second WGC title at its 2018 Masters Victory.
Tyrrell Hatton of England, in his first test since November after a wrist operation, recorded five birdies in 68 to place sixth.