Bubba Watson - who else? - crushed a drive 360 yards on the No. 5 hole, one yard beyond Justin Rose and six yards beyond Russell Henley's 354-yarder, all on the same hole.
39-9 Jason Day hit a 39-foot-9-inch putt at No. 4, the first of his five birdies for the day.
Alexander Noren took down favored Dustin Johnson with seven birdies in an 11-hole stretch, from Nos. 3-13.
Bo Van Pelt and Jason Day both won matches at the 13th green.
Shot of the day
Keegan Bradley's approach at No. 10, from 123 yards, landed on a mound right of the green, spun back and rolled into the cup for an eagle 2.
11 Richard Sterne, in a 1-up victory over Jason Dufner, one-putted 11 holes.
Clutch shot of the day
Charles Howell III made a 21-foot putt at the 16th hole to take a 2-up lead over Tiger Woods.
Sergio Garcia went 20 holes to beat Thongchai Jaidee in sudden death.