The 46-year-old Mickelson had surgery Oct. 19 — three days after tying for eighth in the season-opening Safeway Open — and again Dec. 12. He opened the three-course event at La Quinta Country Club.
Tour rookie Dominic Bozzelli shot a 64 on the Stadium Course at PGA West — the most difficult of the courses — to top the leaderboard. He holed out from 115 yards for eagle on the par-4 14th.
Jhonattan Vegas, the 2011 champion, was a stroke back at 65 along with Harold Varner III, Hudson Swafford and Patton Kizzire. Vegas and Kizzire played PGA West's Jack Nicklaus Tournament Course, and Varner and Swafford were at La Quinta.
Rain fell off and on in the morning and more was expected Friday.
