Bryson DeChambeau takes a one-shot lead into the weekend at the WGC-Mexico Championship, as Rory McIlroy produced a late fightback to stay in contention.
DeChambeau made seven birdies in an eight-hole stretch around the turn to post an eight-under 63 and top the leaderboard at Club de Golf Chapultepec ahead of Patrick Reed and Erik van Rooyen, who marked his 30th birthday by equalling the course record with a second-round 62.
Justin Thomas and Hideki Matsuyama sit two strokes off the pace in a share of fourth spot, while McIlroy birdied three of his last five holes to snatch a two-under 69 and get within three of the lead.
McIlroy held a two-shot lead after the opening day but lost his overnight advantage after Matsuyama opened with four birdies in his opening six holes, only for Thomas to make four consecutive birdies from the 15th to reach the turn with a two-shot advantage.
Thomas drained a 35-foot eagle at the driveable first to temporarily go further ahead, as DeChambeau holed a 15-footer at the 18th for the first of four birdies in as many holes and then added another from six feet at the fifth to get within one.
Matsuyama started his second nine with three straight birdies and followed a 20-footer at the fifth with a close-range gain at the next to temporarily go nine under for the day, only to miss a three-footer to save par at the next and also drop a shot at the eighth to slip two behind.
Thomas dropped a shot at the fourth after clipping a tree with his approach and closed his round with a run of pars to stay at nine under, while DeChambeau made a 20-foot birdie at the sixth and holed a monster 45-footer at the par-three next to temporarily go two ahead.
DeChambeau narrowly missed out on birdies over his final two holes to fall one stroke short of the course record, which Van Rooyen equalled by closing out his blemish-free card by holing from six feet at the par-four last.
Reed reached the turn six off the pace but quickly closed the gap by making a 30-footer at the par-five 11th and adding further birdies over three of his next four holes, before saving par from 10 feet at the 16th and nailing a birdie from double the distance at the next to join the share of second.
Matsuyama signed for a second-round 64 and Thomas carded a five-under 66, while McIlroy was over par for his round until he ended a run of missed chances on the greens by holing a 20-footer at the par-four 12th.
McIlroy made a three-putt bogey from 10 feet at the next but followed a close-range birdie at the 14th with back-to-back gains from the 16th to sit on eight under and in sixth spot.
Tyrrell Hatton and Paul Casey are in a share of seventh alongside Sebastian Munoz, while defending champion Dustin Johnson is strokes back in tied-60th after struggling to a level-par 71.
Watch the WGC-Mexico Championship throughout the week live on Sky Sports. Live coverage continues on Saturday from 5pm on Sky Sports Golf.