World number one Dustin Johnson has withdrawn from the Masters after injuring his back in a fall on Wednesday.
Johnson had gone through a short initial warm-up on the range before reportedly receiving treatment on the back injury he suffered in a "serious fall" in his rented accommodation on Wednesday afternoon.
Johnson then returned to the range and appeared more at ease as he hit shots under the watchful eye of coach Butch Harmon.
The 32-year-old, who missed the 2012 Masters after reportedly injuring his back when lifting a jet-ski, was due out in the final group at 2:03pm local time.
However, the US Open champion then left the first tee and headed into the clubhouse, leaving Bubba Watson and Jimmy Walker to tee off in the final group.
However, the second hole in Augusta has already seen two eagles, courtesy of Phil Mickelson and Martin Kaymer.
Five-time major winner Phil Mickelson picked up two shots on the Par five second hole, before bogeys on the 5th and 6th stalled his progress somewhat, although he still remains below par for the day.
Germany's Martin Kaymer achieved the same feat, having bogeyed the first:
Danny Willett suffered a nightmare start to the defence of his Masters title as world number one Dustin Johnson's participation at a windswept Augusta National remained in doubt.
Willett, who has struggled for consistent form since claiming his first major title 12 months ago, hit a wild opening drive into the trees to the right of the first fairway and needed two shots to escape.
The 29-year-old found the green with his fourth shot and two-putted for a six, making him the first defending champion to start with a double bogey since hole-by-hole records began being collected in 1983.
A similarly wayward drive on the par-five second, which played the easiest hole on the course in 2016, cost Willett another shot and left him five off the pace being set by Ryder Cup team-mates Thomas Pieters and Andy Sullivan.
Pieters, who won a record four points from his five matches in Europe's defeat at Hazeltine, had raced to the turn in 32 with birdies on the second, fourth, fifth and eighth, despite swirling winds making scoring difficult.
The 25-year-old Belgian also picked up a shot on the 10th to reach five under, but then bogeyed the 11th and double-bogeyed the 12th after finding water off the tee.
That dropped him back to two under alongside Sullivan, who had covered the front nine in 35 before making a birdie on the 12th in the group ahead.