Day's victory in a four-way playoff in the 2015 tournament began a big year for the Australian, who won four other tournaments and had 11 top 10 finishes. He is second in the Official World Golf Ranking behind American Jordan Spieth.
Day is also the player whose wife, Ellie, was bowled over by basketball star LeBron James while they sat in courtside seats at a Cleveland Cavaliers game last month. Ellie Day spent the night in a hospital for observation but was otherwise OK.
Day, who missed Wednesday's pro-am because of a bout with the flu, is scheduled to tee off at 9:20 a.m. from the 10th hole at Torrey Pines North, part of a threesome that also includes J.B. Holmes and Harris English.
No. 4 Rickie Fowler and No. 10 Patrick Reed will be part of the next group.
No. 7 Justin Rose and San Diegan Phil Mickelson will tee-off at 10:40 a.m. at the first tee at Torrey Pines South. Eighth-ranked Dustin Johnson will be one group ahead of them.
Ireland's Paul Dunne will make his PGA Tour debut as a professional. As an amateur, Dunne shared the lead after third round of last year's British Open, then shot a final-round six-over-par 78 at St. Andrews to finish in a tie for 30th.
Xander Schauffele, a San Diego State and Scripps Ranch High School alumnus, will be playing in the tournament for the first time.
Spieth bypassed the tournament in favor of the Asian Tour's Singapore Open. Tiger Woods remains sidelined by a hip problem that required surgeries in September and October. Two-time Masters champion Bubba Watson is participating in the PGA Merchandise Show in Orlando, Florida.
Opening ceremonies for the $6.5 million tournament are scheduled at 8:15 a.m. at the first tee on the South Course. Play will begin on the North and South courses at 9 a.m.
On Friday, the players will flip courses. After the cut, the final two rounds will be played exclusively on the South course beginning at 8:30 a.m. both days. The winner will receive $1.17 million.
Parking, with shuttle service, is available for $20 at the Del Mar Racetrack and SeaWorld San Diego during the tournament's four days.
Saturday and Sunday, parking will also be available at The Scripps Research Institute. Prices are $25 and $30, depending on the TSRI lot.