MEXICO CITY (AP) -- Justin Thomas made a hole-in-one and surged into the lead with a 5-under 66 on a Saturday of high entertainment in the Mexico Championship.
Thomas hit a 6-iron from 239 yards that one-hopped into the cup on the par-3 13th. He added a pair of birdies that gave him a one-shot lead over Dustin Johnson, with Phil Mickelson and Rory McIlroy right behind.
Such a world-class leaderboard should have been enough to delight the crowd at Chapultepec Golf Club.
There was so much more.
Johnson, in his debut at No. 1 in the world, was tied for the lead when his second shot on the 16th got stuck in a tree. He walked back to the original spot and hit the next one to 15 feet, and the ball fell out of the tree as he was walking to the green. He made the putt to salvage a bogey and shot 66.
"It happens," Johnson said, and no one knows that better.
Mickelson didn't hit a fairway on the back nine until the 16th hole and at one point took as many drops as he had birdies. Even so, Lefty managed to make three straight birdies until closing with a bogey for a wild round of 68.
He was two shots behind, along with McIlroy, who didn't make a birdie over his last seven holes and shot 70.
At nearly 7,800 feet of elevation, the final round figures to be up in the thin air. That might even include Jordan Spieth, who set the course record with an 8-under 63 and was among a dozen players within five shots of the lead.
It starts with Thomas, the 23-year-old who already has three victories in this PGA Tour wraparound season, two of them at the start of the year in Hawaii. He was hanging around the leaders when he made his hole-in-one on the 13th.
"It looked perfect," he said. "I think I said, 'Go in.' You might as well say it," Thomas said while watching the shot on a TV monitor. "I haven't hit too many shots exactly how I wanted. I liked this result."
Lee Westwood, who has played in more World Golf Championships than anyone since they began in 1999, shot 31 on the back nine for a 66 and was three behind, along with Spanish rookie Jon Rahm, who had a 67.
Mickelson's caddie, Jim "Bones" Mackay, was back to work after coping with a stomach virus on Friday. He didn't walk a straight line the way Mickelson was hitting it off the tee. During one stretch, Mickelson hit one out of eight fairways. He only hit four fairways and eight greens for the round, and he still managed to go into Sunday just two shots off the lead.
"I've shot numbers like this hitting shots like that and salvaging strokes, but I've been playing better than that," Mickelson said, clearly disappointed. "That looks like the way I've hit it the last three years - all over the place and saving shot. I haven't been doing that this year. I wanted to come out here and strike the ball the way I've been striking it, and then to hit it the way I did was disappointing."
McIlroy, playing with Mickelson for the first time ever on the weekend, never got anything going and only had one birdie chance inside 10 feet over the last seven holes. After a birdie on the par-5 11th, he smashed a drive within 60 yards of the green at No. 12 only for his wedge to hit the pin and bounce 20 feet away.
"One of those days," McIlroy said. "Just couldn't really put a few good holes together."
Johnson is trying to become the fifth player to win in his debut at No. in the world, and he still likes his position. He will be in the final group with Thomas and McIlroy. They all live in South Florida and spend plenty of time together.
Johnson started Saturday three shots out of the lead and made up ground in a hurry. He hit 2-iron onto the green on the 316-yard opening hole and made a 20-foot eagle putt, followed with an 18-foot birdie on No. 2 and kept it going with a 35-foot par save on No. 3.
"On the first three holes today, I made more feet of putts than I think I made combined in three rounds," he said.
The greens still perplex him with subtle breaks. According to ShotLink, Johnson had missed seven out of 15 putts from inside 5 feet.
"If it's not the greens - someone is playing goalie up by the hole - the trees are catching my ball," Johnson said.
Spieth went on YouTube on Saturday morning to find video of when he thought he was swinging well, and it paid off. He opened by driving the green and making eagle, and he didn't drop a shot in posting a 63.
What makes a five-shot deficit look more daunting is the names ahead of him - Thomas, Johnson and McIlroy and Mickelson.