The Arnold Palmer Invitational field includes four Irish players.
Seamus Power is the first to tee off at Bay Hill in Florida just after 1pm, Irish time.
Past winner Rory McIlroy, Shane Lowry and Padraig Harrington are all out between 5 and 6.
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Meanwhile, Leona Maguire carded a 2 under opening round of 70 at the HSBC Women's World Championship in Singapore.
She is in a tie for 14th.
American Elizabeth Szokol leads on 8 under.
