Charley Hoffman stormed into a four-stroke lead at a gusty Augusta National at the end of a dramatic Masters opening day that featured a nightmarish nine for Jordan Spieth and the withdrawal of Dustin Johnson before the world number one had played a shot.
Pre-tournament favourite Johnson - a winner in each of his last three starts on the PGA Tour - pulled out just before he was due to tee off on Thursday, having injured his lower back when falling down stairs at his rental home the previous day.
In his absence, a 93-man field faced some of the most testing conditions seen at Augusta in recent years, with only 11 players breaking par amid strong winds.
However, conditions eased somewhat for those out late in the day and Hoffman took full advantage, birdieing five of his last seven holes to complete a sensational seven-under 65.
Hoffman - the world number 52 - was one over after five, but birdied the sixth, eighth and ninth before hitting top form on the inward nine with further gains at the 12th, 14th, 15th, 16th and 17th.
The similarly unheralded William McGirt, from nearby North Carolina and playing this event for the first time, went round in 69, while perennial nearly man Lee Westwood finished in similar fashion to Hoffman - birdieing five holes in succession from the 13th to be one further back.
Those at one under included Phil Mickelson, Justin Rose, Sergio Garcia and Matt Fitzpatrick, who double-bogeyed the last.
World number two Rory McIlroy - seeking to claim the only major title that has so far eluded him - battled back impressively from being three over through eight to shoot an even-par 72, a score matched by the likes of Paul Casey and Thomas Pieters. The latter had been five under through 10, but fell away thereafter.
Playing alongside McIlroy, the highly rated Jon Rahm missed a short birdie putt at 16 and bogeyed the last two to slip to one over alongside Rickie Fowler, who dropped two at the last. Reigning champion Danny Willett also signed for a 73 despite opening with back-to-back sixes, while Jason Day came in at plus two.
Spieth had been one under and tied for the lead through 13, only to slump down the leaderboard courtesy of his second quadruple-bogey in as many rounds at Augusta.
It had been the 12th that caused the 2015 champion pain in last year's final round, as his title defence unravelled spectacularly with a seven at the picturesque par three.
On this occasion, he navigated 'Amen Corner' comfortably but endured misery on 15, After spinning his third shot back into the water, Spieth over-shot the green and played a poor chip before three-putting for an astonishing nine.
The 23-year-old responded admirably, a superb tee shot to 16 setting up a birdie that was followed by a gutsy par save at the last, but he now has much work to do.