After a missed cut in the defence of his Farmers Insurance Open title, Day claimed his first win of the year and eighth overall on the PGA Tour at the Arnold Palmer Invitational, where he beat Kevin Chappell by one shot. Day's victory was wire-to-wire having shot all four rounds under par (66-65-70-70) to finish with a −17 total. He birdied the 17th hole during the final round and had to get up and down from the bunker on the 72nd hole to hold on for the win. Day rose one place in the world rankings to number two, overtaking Rory McIlroy.