Guerrier also birdied the 15th to take a one-shot lead over England's Dan Brown, who made two eagles and five birdies.
"I had the feeling I played the PlayStation on the front nine, it was very nice," Guerrier said. "Of course, it was really nice, but I tried try to stay focused for 18 holes because we know with this wind anything can happen."
The Frenchman had no bogeys at the Real Club de Golf Sotogrande in southern Spain.
"When you are playing like that and everything goes your way, you take everything and it was a great feeling, of course," he said.Â
"It looks easy from the outside but it's very tough to stay in the present. Sometimes the emotion is too high and you try to calm down a little bit, but at the same time you try to enjoy it as well, so it's a good balance."
Jon Rahm playing in his third European tour event in the past four weeks, shot a 2-under par in a round that included five birdies and three bogeys. He was tied for 38th.
Rahm, No.14 in the world, is the top-ranked player in the field this week, which marks the final tournament of the year on European soil for the European tour.
The last tournaments are in South Korea, Abu Dhabi and Dubai.The only other top 50 player in the world ranking is Thriston Lawrence (69).
Jorge Campillo of Spain was two shots off the lead after his bogey-free 64. Australia's David Micheluzzi has withdrawn from the event.
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