Bill Haas holds a one-shot lead over defending champion Adam Scott, Bubba Watson and Louis Oosthuizen after round one of the 78th Masters at Augusta.
The 31-year-old American fired a four-under-par 68 on a difficult day for scoring under a hot Georgia sun.
Tournament favourite Rory McIlroy hit a one-under 71 and said the course was the toughest he has seen on a Thursday.
Three-time champion Phil Mickelson was among the big names to struggle and had a triple bogey on the seventh in a 76.
Haas, whose great uncle Bob Goalby won the Masters in 1968, birdied the last to take an unlikely lead as he chases a first major title, although he should be able to cope with the pressure having won the $10m FedEx Cup in 2011.
"I know that I can't expect too much," said the son of former PGA Tour stalwart Jay Haas. "You've just got to go out there and keep playing golf, try to hit that fairway on number one."
Scott, who became the first Australian to win the Green Jacket last year, went out in 33 and hit the front at four under after 10.
But his "weak" nine-iron in a swirling wind at the short 12th caught the bank in front of the green and rolled into Rae's Creek. He found the putting surface with his third after pitching from the fairway but took two putts from five feet for a six.
The 33-year-old reached the green in two on the par-five 13th but was unable to capitalise and three-putted for par after a long wait as playing partner Jason Dufner, the US PGA champion, ran up a nine.
Scott picked up a shot on the bunkerless 14th and parred home to lay a decent platform in his quest to become only the fourth player to win back-to-back Masters after Jack Nicklaus (1965-66), Nick Faldo (1989-90) and Tiger Woods (2001-02).
"I played really well from tee to green, except for a poor shot on 12. I perhaps left a couple out there on the par fives, but it's certainly something to build on," said Scott.
"I think winning here calms you down. It was the calmest start I have ever had. I had a fantastic response from the patrons."
American left-hander Watson, who beat Oosthuizen in a play-off to clinch the Green Jacket in 2012, birdied the third, 13th and 15th and parred the other 15 holes to end three under.
Former Open champion Oosthuizen, who fired a magnificent albatross two on the par-five second hole at Augusta two years ago, was three under after nine and stayed that way at the finish after an up-and-down back nine.
McIlroy, chasing a third major title and first Masters, was two under after five but tripped up with a bogey at the long eighth to go out in 35.
He dropped another shot after three-putting the 12th from some distance but made birdies at the 13th and 15th before catching the fairway bunker up the last. He was able to make the green with his second but three-putted again from 30ft for a bogey to end in a tie for 12th.
"It was a good day. It was solid," said the 24-year-old Northern Irishman, who blew a four-shot lead on the final day in 2011. "I think that they set the course up very difficult. Some of the pin positions were tough to get close to.
"The greens are firming up. The wind was all over the place. Anything under par was a good score."
Mickelson, bidding to join the absent Woods and the legendary Arnold Palmer on four Green Jackets, had a disastrous seventh hole after parring the first six.
He was on the fringe of the green in two shots, 30 feet from the hole, but his putt raced past the pin and off the green and he then took another four shots.
Mickelson fought his way back to one over after 13 but handed a shot back on 14 and double-bogeyed the par-five 15th after laying up in front of the green and seeing his third shot spin back off the bank into the water.
The 43-year-old Open champion had three pars to finish but cut a dejected figure on the 10th anniversary of his breakthrough major win at Augusta.
"I've got a lot of work to do just to make the cut. So I've got some issues," said Mickelson, who signed for his worst opening round at the Masters since 1997 when he missed the cut.
"I know it's hard to say that, but I actually played well and I just made a lot of little mental errors."
Seven players ended two-under, including Brandt Snedeker, who has twice played in Sunday's final group at Augusta, and Kevin Stadler, who was making history alongside dad Craig as the first father and son to play in the same Masters.
Sweden's Jonas Blixt, who was also in the group on 70, led the European challenge as world number three and fellow Swede Henrik Stenson ended one over with Lee Westwood, while US Open champion Justin Rose battled to a 76.
England's 19-year-old amateur debutant Matthew Fitzpatrick, playing with Scott and Dufner, also ended four over alongside countryman and fellow amateur Garrick Porteous, Ian Poulter and former champion Sandy Lyle.
Among the big names to struggle on the opening day were former champion and last year's runner-up Angel Cabrera (78), England's Luke Donald (79), who was assessed a two-shot penalty for grounding his club in a bunker on the ninth, and American Dufner, who carded 80 after coming home in 44 shots.