Jacob Bridgeman birdied five of the last seven holes to grab a one-stroke lead after Thursday's opening round of the US PGA Tour's 3M Open.
The 24-year-old American fired an eight-under-par 63 to finish one stroke ahead of Canada's Mackenzie Hughes after 18 hopes at TPC Twin Cities in Blaine, Minnesota.
France's Martin Trainer and Americans Andrew Novak and Patrick Rodgers shared third on 65.
Bridgeman, a PGA rookie ranked 206th in the world, managed his best tour finish by sharing 14th at last month's Canadian Open but missed the cut in three prior July starts.
"I struggled with my mental game the last three weeks. I was in kind of a rough place," Bridgeman said. "Never had struggles with my confidence until these last few weeks and I told a couple people I felt like I've been kicked in the face.
"But it's all new to me, I'm a rookie out here. I'm still pretty young. I have to remind myself that. These are all new courses that I'm facing every week. I have to learn them.
"I had to change my mindset, reset this week, take a couple days of rest and I thought I did well today."
Bridgeman opened with a tap-in birdie, added birdie putts just beyond five and seven feet at the fifth and par-5 sixth holes respectively then sank a 34-foot birdie putt at the par-3 eighth before closing the front nine with her lone bogey of the day.
"Made a couple putts I probably shouldn't have, but I also hit it pretty nice," Bridgeman said.
"Hit my driver well and all around it was a good round. I had really one bad swing that I made a bogey on nine, but other than that I'm pretty confident that I can play another good round tomorrow."
Bridgeman added a seven-foot birdie putt at the par-5 12th, a 20-footer to birdie the par-3 13th and a tap-in birdie at 14, then followed two pars by sinking a 41-foot blast from a bunker at the par-3 17th and tap-in at the par-5 18th for two closing birdies.
The event marks the penultimate PGA regular-season tournament, with players trying to accumulate points to reach next month's playoffs.