Bubba Watson continued his impressive bid for a second Masters title in three years in the early stages of the second round on Friday.
Watson was the only player in the 97-strong field to card a bogey-free round on a testing opening day at Augusta National, the left-hander's 69 containing three birdies and 15 pars.
And the flamboyant world number 12 had still not dropped a shot by the time a birdie on the seventh took him into a share of the lead with Bill Haas on four under par.
Australian Marc Leishman had briefly held the lead on five under par when he started his round with birdies at the first three holes following an opening 70.
But the 30-year-old, who was in the penultimate group on the final day last year and famously celebrated as playing partner Adam Scott birdied the 72nd hole, followed that with bogeys at the fourth and fifth.
Leishman was joined on three under by Masters rookies Kevin Stadler and Jonas Blixt, who had both carded opening rounds of 70 and birdied the par-five second today.
And former Open champion Louis Oosthuizen, who lost a play-off to Watson in 2012, was two under after 11 holes of his round following two bogeys and one birdie.
Conditions were again perfect for the early starters, but recent history suggested the odds were against those not already high on the leaderboard.
The last eight winners of the year's first major championship had been inside the top 10 after the first round, which was good news for the likes of Watson and defending champion Scott, who was among the late starters.
Rory McIlroy rewrote numerous records in his eight-shot victories in the 2011 US Open and 2012 US PGA Championship, so the 24-year-old would not be too worried about being joint 12th overnight.
However, the Northern Irishman was concerned about being in the last group out just before 2pm local time, with tough pin positions, firm greens and wind forecast to gust up to 20mph set to make life difficult.
The top 50 players and ties will make the halfway cut, along with any player within 10 shots of the lead.
Watson finally dropped his first shot of the week on the ninth when his approach flew the green and left him with an almost impossible third shot to a severely sloping green.
That dropped him back to three under par and one behind Oosthuizen, Blixt and Stadler, Oosthuizen having holed from just five feet for an eagle on the par-five 13th.
Stadler, making history with dad Craig as the first father-son combination to play in the same Masters, had birdied the fifth, while Blixt had picked up a shot on the third.
After his eagle at the 13th, Oosthuizen experienced the flip side of Augusta's par fives, running up a triple-bogey eight on the 15th after going over the green with his approach and then pitching back across the green into the water.
That left Stadler and Blixt in the lead on four under with Denmark's Thomas Bjorn just a shot off the lead as he compiled the round of the day so far.
Bjorn shot 73 on Thursday and was only level par after 13 holes on Friday before birdies on the 14th, 15th and 16th vaulted him up the leaderboard.