Dominic Bozzelli earned a one-stroke at the CareerBuilder Challenge as veteran Phil Mickelson starred on his return to the PGA Tour.
Bozzelli opened with an eight-under-par 64 at La Quinta Country Club on Thursday.
The 25-year-old American was flawless in La Quinta, California as he holed six birdies and an eagle without dropping a shot.
Patton Kizzire, Hudson Swafford, Jhonattan Vegas and Harold Varner III are a shot further back.
However, all eyes were on Mickelson on the Tour's early season west coast swing.
Mickelson, 46, had last played at the Safeway Open in October, having twice undergone surgery for a sports hernia.
But the five-time major champion made his long awaited comeback, shooting a fine four-under 68.
Despite a lack of practice, Mickelson had five birdies to go with a birdie as he ended the opening round four strokes adrift of Bozzelli, alongside two-time tournament winner Bill Haas.
In a relatively thin field, defending champion Jason Dufner posted a one-under-par 71.