The gusting winds intensified as the afternoon wore on at the TPC-Doral course, but Scott and Dufner survived to move in front by two shots. Both players carded only one bogey.
The most recent of Scott's eight PGA Tour victories came at last year's WGC-Bridgestone Invitational. Dufner's tour highlight came last August when he lost in a playoff to Keegan Bradley at the PGA Championship after seemingly having the tournament wrapped up late in the fourth round.
Woods eagled the opening hole, but struggled finding the proper distance on a series of long putts and finished with a 72. Mickelson shot the same score with a double bogey and two bogeys on his card.
McIlroy, the winner last week at the Honda Classic after finishing as the runner-up the week before at the WGC match play event in Arizona, had four bogeys his round of 73.