Golf World No.1 Dustin Johnson has withdrawn from the Masters after injuring his lower back in a fall down stairs at his rented Augusta house.
The big-hitting American had arrived at the course and was scheduled to tee off this morning, but withdrew after walking off the first tee.
Johnson became the first No.1 player to miss a major since Rory McIlroy at the British Open two years ago at St Andrews.
Johnson was favourite to win his maiden major title after winning his last three tournaments.
Meanwhile Australian Adam Scott, with New Zealand's Steve Williams as caddie, has struggled to capitalise on vastly improved ball- striking midway through his opening round.
The 2013 Masters winner's swing looks to be in good form for the year's first major but Scott is currently one-over-par through 10 holes on Thursday.
The first Australian to don the green jacket sits six back from current leader Thomas Pieters, with the Belgian youngster on a hot run at five-under through 10 holes.
He holds a three-shot advantage over world No.8 Rickie Fowler, while a host of players including three-time Masters winner Phil Mickelson are a shot back at one-under.
Struggling with his ball-striking for the first three months of 2017, 36-year- old Scott opened his 2017 Masters with a bogey at the difficult par-4 first hole.
He bounced back with superb shots to set up birdie chances at the third, fifth, sixth and eighth holes but registered only one at the par-3 sixth before another dropped shot at the par-4 ninth dropped his total to one-over.
Also one-over the card is world No.3 Jason Day, who suffered a bogey at the third and is through six holes.