Sergio Garcia of Spain shot a fine six-under 65 to hold a two-stroke lead after the third round of the PGA tour's Deutsche Bank Championship in Boston.
Swede Henrik Stenson's 66 took him within two shots of Garcia while Canada's Graham DeLaet produced a sparkling nine-under 62 to sit one further adrift along with American Steve Stricker (63).
After enjoying much of the limelight as playing partners for the first two rounds, world number one Tiger Woods and British Open champion Phil Mickelson had disappointing days.
Mickelson had three bogeys on the back nine and his second straight even-par round left him 11 behind Garcia.
Woods found the fairway just seven times in his one-over 72 to be six-under, tied in 47th place.