A spectacular hole-in-one helped Justin Thomas reach the top of a star-studded leaderboard after an incident-packed third round of the WGC-Mexico Championship.
Thomas, who won back-to-back events in Hawaii at the start of the season, holed out with a six iron from 232 yards on the 13th at Chapultepec Golf Club, his tee shot pitching around 15 feet from the flag and taking a big bounce before plummeting straight into the hole.
The world number eight also carded five birdies in a 66 to finish 12 under par and a shot ahead of world number one Dustin Johnson, with halfway leader Rory McIlroy and Phil Mickelson a shot further back.
Johnson wiped out his three-shot overnight deficit by making an eagle on the first and birdie on the second, the US Open champion also picking up shots on the sixth, 13th and 15th.
However, Johnson's approach to the 16th then stuck up in a tree and was declared lost, only for the ball to drop out of the branches after the 32-year-old had already played another onto the green.
" I kind of hit it a little thin so it didn't get up high enough and I heard it clip the tree," Johnson said in a post-round interview broadcast on Sky Sports. "I figured it would be in or just short of the bunker but we couldn't find it.
"I was just laughing. If it's not the greens it's something else that's going against me right now but I'm playing really well, I just have to keep giving myself looks and see what we can go out and shoot tomorrow."
In contrast, Mickelson enjoyed several strokes of good fortune on the back nine and made the most of them with a hat-trick of birdies from the 15th in a hugely eventful 68.
The left-hander looked set to lose a ball after a wild drive on the 10th, only for a spectator to say that he had seen a ball picked up from the search area, thereby allowing Mickelson a free drop.
After making par there, Mickelson then hit further bad tee shots on the 11th and 12th, but each time received a free drop from the bushes as his stance was hampered by a sprinkler head.
Playing partner McIlroy, who is making just his second start of the season after suffering a stress fracture to his ribs, made the ideal start with a birdie on the first, but dropped shots on the next two holes.
The 27-year-old, who can regain the world number one spot with a victory if Johnson finishes outside the top four, bounced back with a birdie on the sixth, but bogeyed the eighth before holing from 20 feet for birdie on the ninth.
McIlroy also birdied the 11th after a superb pitch from left of the green but was unable to make any further gains before eventually signing for a 70.
Ryder Cup team-mate Lee Westwood was a shot behind after a superb back nine of 31 in his 66, with fellow Englishmen Tommy Fleetwood and Tyrrell Hatton on eight under after rounds of 66 and 68 respectively.
Two-time major winner Jordan Spieth carded a course-record 63 to finish seven under par.