Scott was trying to join the list of 22 players who have shot 63 in a major. After posting birdies on five of his first seven holes on the back nine, he finished par-bogey.
Scott holds a one-shot lead over a pair of former major championships in Paul Lawrie and Zach Johnson. Reigning Masters Tournament champion Bubba Watson is tied at 67 with major champions Ernie Els, Graeme McDowell and Tiger Woods. With birdies on four of his seven holes, Woods got off a to a fast start. He shot 1-over the rest of the way.
Augusta native Charles Howell shot 1-under on the front nine and is still on the course.