MEXICO CITY (AP) Justin Thomas started and ended his round with bogeys. He was at his best in the 16 holes between, running off eight birdies for a 6-under 65 that gave him a one-shot lead Saturday in the Mexico Championship.
At this World Golf Championship, that doesn't mean all that much going into the final round.
Thomas was five shots behind in the middle of his front nine at Chapultepec Golf Club. He wound up with a one-shot lead over Patrick Reed and Erik Van Rooyen of South Africa.
No one illustrated how quickly fortunes can change like Jon Rahm, who started the third round 10 shots out of the lead and goes into Sunday in the penultimate group, just four shots behind.
Rahm opened with six birdies in seven holes - four of those birdies from inside 4 feet - and really excited the crowd with a gap wedge on the par-3 17th that took one big hop and disappeared into the cup for an ace. That carried him to a 61 to break the course record, and it was his low round of his young career.
Better yet, the Spanish player is in the mix in Mexico.
''I'm just really happy that after the first two days I'm going to have a legitimate chance tomorrow without needing to shoot 59 or something like that,'' Rahm said.
It starts with Thomas, going after his third victory of the PGA Tour season. After a sloppy start with a bogey on the reachable par-4 first hole, he was solid the rest of the way until the end, when his drive went into the trees and he missed a 6-foot par putt.
Thomas was at 15-under 198 at the tournament he lost in a playoff two years ago.
Reed matched him birdie-for-birdie on the back nine and was tied until he went into a bunker on the 18th hole, blasted out weakly from the heavy sand to the fringe and made bogey for a 67.
Van Rooyen didn't flinch, not when Bryson DeChambeau got off to a hot start, not while trying to keep pace with Thomas and Reed. He had a 67, highlighted his fourth chip-in of the week and driving the 379-yard second hole in high altitude to about 12 feet for eagle.
Rory McIlroy couldn't keep pace, taking bogey on the par-5 sixth when he went for the green in two and was left an impossible play from over the green to a back pin,. He made bogey on the 14th, and didn't make a birdie coming in. McIlroy played the par 5s in even par and had to settle for a 68.
Even so, he was tied with Rahm and DeChambeau (70) at 11-under 202.
Tyrrell Hatton and Paul Casey each had 66 and were five shots behind.
The disappointment belonged to DeChambeau, who started birdie-eagle, the latter when driving to 6 feet on the second hole. He was 4 under through five holes and leading by three when his third to the par-5 sixth came up short and spun back into the water, leading to double bogey.
And then it got ugly at the end. He missed the green on the 13th and made bogey. He missed a 5-foot par putt on the 14th, angrily hammering down imperfections in the green after the miss. He three-putted for par on the par-5 15th and then missed another 4-foot par putt on the 17th.