MEXICO CITY — Bryson DeChambeau kept making so many birdies in the Mexico Championship that when he rolled in his ninth one from 45 feet, all he could do was throw his hands in the air in pure wonder.

He wasn’t alone Friday in making birdies, although Rory McIlroy would like to have joined the party.

DeChambeau made seven birdies in an eight-hole stretch at Chapultepec Golf Club for an 8-under 63, giving him a one-shot lead over Erik van Rooyen of South Africa and Patrick Reed at the halfway point of this World Golf Championship. DeChambeau was at 11-under 131.

Van Rooyen, who played college golf at Minnesota, celebrated his 30th birthday by making nine birdies to tie the course record with a 62. Reed made five birdies on the back nine for a 63

Justin Thomas ran off four straight birdies to end the back nine, and then holed a 35-foot eagle putt to build a three-shot lead through 10 holes. That was gone in a matter of four holes as player after player kept rolling in putts on a day with much less wind and far better scoring. The average score 70.28, more than two shots better than Thursday.

Hideki Matusyama was 9 under for his round through 15 holes and had a 20-footer birdie attempt from the fringe on the par-3 seventh. He missed that 3 feet to the left, then missed the next one. He bogeyed the next hole, too, and had to settle for a 64. That left him at 9-under 133, along with Thomas.