Joaquin Niemann set the pace on day one of the Sentry Tournament of Champions, topping the leaderboard with a seven-under round of 66.
The Chilean 21-year-old made a flurry of four birdies between the fourth and ninth holes before adding a further three gains after the turn in a bogey-free round.
The performance earned Niemann - winner of A Military Tribute at The Greenbrier in September - a one-shot lead over 2017 champion Justin Thomas, whose five birdies on the back nine saw him soar up the leaderboard.
Matt Kuchar and Rickie Fowler are two shots off the lead, the former having eagled the fifth.
Defending champion Xander Schauffele, Jon Rahm, and Patrick Cantlay are among a group of five players tied at four under.
In an eventful opening round, Dustin Johnson posted five birdies, four bogeys, an eagle and a double bogey to end the day in a tie for 16th at one under.
Graeme McDowell is one one over, with five bogeys and four birdies in his round.