Roberto Castro carded a 10-under-par 62 to earn a two-stroke lead after day one of the Sanderson Farms Championship in Mississippi.
The American, 30, sank no fewer than 10 birdies in a dazzling opening-round in Jackson as he sits two shots clear of Aaron Baddeley and Bryce Molder.
England's Brian Davis is also in contention after shooting a first-round 65 as he sits level with Adam Hadwin on seven-under.
Jhonattan Vegas and Graham DeLaet are two of five players back on six-under, while fading light saw Tyrone Van Aswegen and Mark Hubbard cut their opening rounds short.
Van Aswegen sits on five-under after 15, with his playing partner Hubbard is two strokes back as they prepare to finish their round on Friday morning.
