Augusta - Jordan Spieth took up where he left off 12 months ago with a pace-setting 66 on Thursday as he attempted to become just the fourth man to successfully defend the Masters crown.
The Texan, just 21 at the time, was the first wire-to-wire winner in 40 years at Augusta National last year, and his bogey-free opener brought up the possibility he could do so again.
Only Jack Nicklaus, Nick Faldo and Tiger Woods have managed back-to-back wins in the Masters.
Spieth, who opened with an eight-under 64 en route to his record-matching victory last year, reached the turn in 31 after birdies at the fourth, sixth and eighth and he added three others down the back nine at 10, 13 and 18.
Taking advantage of fine early playing conditions as the 80th Masters got underway, Spieth was in the clubhouse early and able to sit back and see if top rivals Jason Day and Rory McIlroy could keep pace with him during the afternoon's action.
If he stays atop the leaderboard, it would mean that he has been the leader after six of the nine Masters rounds he has played at Augusta National since his debut in 2014.
Underlining the quality of Spieth's round was the fact that the only other player to score in the 60s among the early starters was playing partner Paul Casey, who fired birdies at 13, 15 and 16 en route to a 69.
Three players -- Americans Kevin Streelman and Charley Hoffman and England's Lee Westwood were next best in the clubhouse on 1-under 71.
Out on the course, though, the pack was on the charge.
Justin Rose was at 3-under after 13 holes with two-time champions Bubba Watson and world number one Day on the same mark approaching the turn.
Australian Day, the tournament favorite, was looking to win back-to-back majors after his triumph in the PGA Championship last August.
He started quietly, but then signaled his intentions with a superb eagle at the par-5 second and followed up with a birdie at the fifth.
McIlroy, 26, was looking to become just the sixth player after Woods, Nicklaus, Gary Player, Ben Hogan and Gene Sarazen to win all four majors. He was the final player to tee off on the day.
The Northern Irishman, without a tournament win this year, birdied the second, but the wind was getting up to make low scoring more difficult for the late starters.
Three-time former winner Phil Mickelson was 1-over after 14 holes and 2013 winner Adam Scott was 2-over after 13.
There were struggles for another top American hope, Rickie Fowler, who was moving along smoothly at even par through nine, but then bogeyed 10 and took an eight at the par-5 13th where he hit into Rae's Creek in front of the green.
The American went into the water again at the 16th for a double bogey and finally limped in with an 80, leaving him with a mountain to climb just to make the cut.
But that was nothing compared to the horrors that beset four-time major winner Ernie Els, who had an astonishing 10 at the par-4 first hole, virtually wrecking his tournament in the space of a few minutes.
It was the worst-ever score at the opening hole in the history of the tournament.
Golf legend Tom Watson, playing his 43rd and final Masters at the age of 66, impressed with a 74 that left him in with a chance of making the cut for the weekend.