Argentina's Emiliano Grillo, finishing in near darkness, fired an eight-under par 63 to seize a four-stroke lead in the sunset-halted second round of the PGA Mayakoba Classic.
The 28-year-old South American, whose lone tour title came at the 2015 Frys.com Open, stood on 13-under 129 after 36 holes at Playa del Carmen, Mexico.
"Played well all day, made some good putts and hit it close," Grillo said. "All I can ask for."
Americans Tony Finau and Tom Hoge shared second on 133 with Scotsman Russell Knox another stroke adrift.
With play starting an hour late due to bad weather, there were 18 players who were forced to finish their second round on Saturday morning.
The lowest among them was American Andy Ogletree, making his pro debut. He was 5-under for the round and 7-under for the tournament with three holes to finish.
Grillo is confident he can capture the title by matching his performance so far at the weekend.
"I did my work in the first few days," Grillo said. "I've just got to keep doing the same work another two days - I'm pretty sure (that) will get it done.
"It's kind of hard to keep it this way for four days, so I'm just going to again just hit it from the fairway and try to hit it close again."
Grillo opened and closed his front nine with birdies and added another at the par-3 fourth, but took his lone bogey at the par-3 10th.
He responded by reeling off three birdies in a row, starting with a tap-in effort at the par-4 12th and closing with a 10-foot birdie putt at 14.
He then dropped his approach at the par-4 17th and made a birdie putt and closed with a par to finish the low round of the week.
"Everything worked today," Grillo said. "Played from the fairway, hit it close and when it wasn't too close, I made putts. It was one of those days."
Finau, seeking his second PGA title after the 2016 Puerto Rico Open, started on the back nine and would have owned second alone but closed with a bogey at the ninth to shoot 66.
"Made a lot of up and downs when I needed to and I was able to score on the holes when I wasn't able to hit it in the fairway," Finau said.
"I just seem to have the right combo for this golf course this week. Hopefully that continues. Just have to put it in the fairway. If you do you will have a lot of good looks."
Finau, who needed only 24 putts, has made 168 career starts with only the lone win while Hoge has 165 PGA starts without a victory.
Leading scores from Friday's second round of the PGA Mayakoba Golf Classic at Playa del Carmen, Mexico (par-71, USA unless noted, halted by darkness with 18 players forced to finish on Saturday):
129 - Emiliano Grillo (ARG) 66-63
133 - Tom Hoge 66-67, Tony Finau 67-66
134 - Russell Knox (SCO) 65-69
135 - Joel Dahmen 68-67, Aaron Wise 67-68, Kyle Stanley 68-67
136 - Carlos Ortiz (MEX) 67-69, Brendon Todd 67-69, Nate Lashley 67-69, Camilo Villegas (COL) 70-66, Lucas Glover 71-65, Akshay Bhatia 67-69, Patrick Rodgers 70-66, Viktor Hovland (NOR) 67-69, Joaquin Niemann (CHI) 66-70
137 - John Huh 70-67, Corey Conners (CAN) 71-66, Tyler Duncan 70-67, Jason Dufner 69-68, Vincent Whaley 71-66, Adam Long 70-67, Hunter Mahan 68-69