Erik van Rooyen rides two eagles to PGA Tour Mexico Open lead
Van Rooyen, who added five birdies with just one bogey, gave himself a seven-footer for eagle at the par-five sixth in Puerto Vallarta. His eagle at the 12th was more spectacular - a chip-in from 70 feet.
"Twelve's a funky one because we played it into the wind in the practice round and you obviously can't get there for two. So today was downwind, smash three-wood and just a beautiful little pitch," he said.
"It's something I've been working really hard on and to see that go in, it feels good."
After his only bogey at 15, van Rooyen birdied the par-five 18th to finish one stroke in front of Finland's Sami Valimaki.
South African MJ Dafue, Sweden's Henrik Norlander, American David Lipsky and Chile's Cristobal Del Solar were tied for third on 65.
Van Rooyen is gunning for a second PGA Tour title in Mexico, having won the World Wide Technology Championship at Los Cabos last November for a second title to go with his 2021 Barracuda Championship victory.
One day after his 34th birthday, the South African said he believes he is "stepping into my best golf."
"Had a few injuries the last few years and I'm finally healthy and good golf's starting to show up," he said. "So I like to think the best golf is still ahead of me."
Valimaki seized solo second with an eagle at the seventh - his third-from-last hole. The 25-year-old, chasing his first title, also had six birdies with one bogey.
Del Solar is riding high after firing a stunning 57 on the developmental Korn Ferry Tour event in Bogota two weeks ago.
It was the lowest round ever at a US PGA Tour-sanctioned event, lowering the previous record of 58 shot by Jim Furyk at the 2016 PGA Tour Traveler's championship and by Germany's Stephan Jaeger in a 2016 Korn Ferry tournament.
Del Solar said his recent form is an indication that he's on the right path toward becoming a US PGA Tour regular.
"Obviously I want to be playing the PGA Tour, but last year was my first year on the Korn Ferry and I think I learned a lot," said Del Solar, who has a sponsor's invitation this week.
"The competition on the Korn Ferry, I mean, it's the same as the PGA Tour, the guys are so good. Obviously you've got the top in the world playing the PGA Tour, so that's where I would like to be and compete against them."