The weather forced a number of players to get a late start.
The clubhouse leader was Sean O'Hair at 5-under 67.
"It's been a while since I had a good start to an event, so it's nice to just feel positive about what happened today instead of fighting to make the cut," O'Hair said. "Instead of putting a lot of pressure on myself, I am just trying to get back to playing my game and let the results come."
Masters champion and world No. 2 Phil Mickelson -- who returned to action this week -- was 3-under 69, tied with a group that included Sergio Garcia, Stuart Appleby and Fred Couples, the 1998 winner and two-time Memorial runner-up.