Former Masters Tournament champion Zach Johnson began the 142nd Open Championship in the same imperious style as last year's event.
Johnson, a 2007 winner at Augusta, carded a five under 66 to set the clubhouse lead at Muirfield.
The American Ryder Cup star, who opened last year's tournament at Royal Lytham with a 65, seemed to breeze round after an eagle at the 559 yard fifth kick-started his charge up the leaderboard.
After a birdie at the third, he picked up four shots in three holes to reach the turn in 31 and a 20 foot birdie on the 12th took him to six under before handing back a stroke two holes later and then parring his way home.
Spaniards Rafael Cabrera-Bello and Miguel Angel Jiménez were already safely in the clubhouse on four and three under respectively.
The latter, aged 49, had opened up with three successive birdies as hard fairways, sun and light winds presented more scoring opportunities than usual.
By the turn he was five under, having gone out in 31, and had a three shot lead before giving strokes back coming home.
Cabrera-Bello birdied the par five 17th to restore himself to four under having bogeyed the 15th.
The 1998 Open Champion Mark O'Meara blazed a trail for the veterans in the field with the 56 year old four under through 13 holes a week before he returns to Royal Birkdale for the Senior Open.
Americans Dustin Johnson and Brandt Snedeker carded three under 68s with compatriot Phil Mickelson, looking for an Open double after winning the Scottish on Sunday, was a shot further back.
Lee Westwood, still seeking his first major, began well with two birdies in his first four holes.
Defending champion Ernie Els, looking for his second Claret Jug at Muirfield and third overall, finished three over with US Open champion Justin Rose one stroke worse off.
Johnson revealed afterwards that last week's near miss at the John Deere Classic had spurred him.
It was a pleasing return to action for Johnson, who was agonisingly beaten in a sudden-death play-off by 19-year-old Jordan Spieth in Silvis, Illinois, on Sunday.
The 37 year old said: "I think this game demands resilience.
"It demands resilience on the golf course, each round, each hole, and day to day.
"But it also demands it week to week, and that just comes with experience.
"That certainly comes with embracing what's happened and then also throwing it behind you and plodding along to the future.
"If anything from last week, what I've embraced is the fact that I'm playing great and I can put that into play, and I'm certainly somewhat confident in what I'm doing, confident in my routines."
Shiv Kapur was the only late starter threatening to overhaul the leaders, the Indian chipping in twice to card six birdies in his first seven holes, while Tiger Woods was battling back after a poor start.
The World Number One, without a Major win since 2008, hooked his tee shot on the first into thick rough and played a provisional ball before his original was found.
After a penalty drop and third shot into a greenside bunker he escaped with a bogey five and was still one over at the turn, before birdies at the tenth and 11th took him into red figures.
