Justin Thomas makes an ace and takes lead in Mexico

Dustin Johnson of the U.S. hits a ball on the 1st hole in round three of the Mexico Championship at Chapultepec Golf Club in Mexico City, Saturday, March 4, 2017. All but one of the world's top 50 golfers are contesting the World Golf Championship PGA event, which this year relocated to Mexico City from the Trump National Doral Resort in Florida. (AP Photo/Eduardo Verdugo) (The Associated Press)

Rory McIlroy, of Northern Ireland, putts the ball on the 17th hole green in round two of the Mexico Championship at Chapultepec Golf Club in Mexico City, Friday, March 3, 2017. All but one of the world's top 50 golfers are contesting the World Golf Championship PGA event, which this year relocated to Mexico City from the Trump National Doral Resort in Florida. (AP Photo/Eduardo Verdugo) (The Associated Press)

Rory McIlroy, of Northern Ireland, prepares to putt on the 17th hole green in round two of the Mexico Championship at Chapultepec Golf Club in Mexico City, Friday, March 3, 2017. All but one of the world's top 50 golfers are contesting the World Golf Championship PGA event, which this year relocated to Mexico City from the Trump National Doral Resort in Florida. (AP Photo/Eduardo Verdugo) (The Associated Press)

Justin Thomas made a hole-in-one and surged into the lead with a 5-under 66 on a day of high entertainment in the Mexico Championship.

Thomas hit a 6-iron from 239 yards into the cup on the par-3 13th Saturday. He wound up at 12-under 201 and a shot ahead of Dustin Johnson. Thomas already has three victories this season.

Johnson thought only the greens were conspiring against him. On Saturday, it was a tree. His shot on the 16th hit a tree and never came out. Right after he hit his fourth shot, the ball fell from the tree. Johnson salvaged a bogey and finished with a 66.

Phil Mickelson (68) and Rory McIlroy (70) were two behind, setting up the potential for a dynamic final round.