The Australian withdrew from the tournament about an hour before he was supposed to tee off on Thursday.

Day, the No.33 in the world, had high hopes, coming off a week of contending at the Arnold Palmer Invitational until a double-bogey on the 16th hole of the final round ended his hopes.

Day won The Players in 2016 when he was the world's No.1 player. 

The PGA Tour did not immediately disclose the nature of his illness.

Day was replaced by Danny Walker, which gives the tournament 26 players who are competing at TPC Sawgrass for the first time.