England's Matthew Fitzpatrick has taken a share of the early lead at the Arnold Palmer Invitational after carding a first-round 67.
The 22-year-old, ranked 30th in the world, birdied three of his last nine holes to end the day on five-under-par.
Argentina's Emiliano Grillo had earlier recovered from two early bogeys to reel off seven birdies in cold conditions to set the clubhouse lead at Bay Hill.
He and Fitzpatrick top the leaderboard and sit one clear of England's Paul Casey, while Rory McIlroy struggled by opening with a two-over 74.
World number two Jason Day made a solid start to the defence of his title with a two-under opening round of 70 in near-freezing temperatures.
The tournament is being held for the first time since Palmer died last September at the age of 87.
Giuseppe Labellarte
