Masters favourite Dustin Johnson took a serious fall on a staircase Wednesday and injured his lower back, and his manager said it was uncertain whether the world's No. 1 golfer would be able to play the tournament.

It was a stunning development on an otherwise quiet day at Augusta National, where the course was shut down at 1:30 p.m. because of storms.

The real calamity struck a few hours later.

David Winkle, his manager at Hambric Sports, said Johnson fell on the stairs at the home he is renting in Augusta.

"He landed very hard on his lower back and is now resting, although quite uncomfortably," Winkle said in an email. "He has been advised to remain immobile and begin a regimen of anti-inflammatory medication and icing, with the hope of being able to play tomorrow."

What might help Johnson is that he is in the last group for the opening round, scheduled to tee off at 2:03 p.m. with two-time Masters champion Bubba Watson and PGA champion Jimmy Walker.

Johnson had been scheduled to attend the Golf Writers Association of America annual dinner Wednesday night to accept its award as male player of the year. He was coming off a season in which he won the U.S. Open for his first major, was voted PGA Tour player of the year for the first time, won the PGA Tour money title and captured the Vardon Trophy for the lowest adjusted scoring average.

Rickie Fowler this week described the 32-year-old American as a "freak of nature."

Winkle on Tuesday said Johnson was in "as good a shape as I've ever seen him in every aspect of his game and his life."

Johnson has had his share of mishaps in a major but not before a major even started.

Two years ago, Rory McIlroy was playing soccer when he ruptured ligaments in his ankle a few weeks before he was to defend his title in the British Open at St. Andrews when he was No. 1 in the world.

But this was far different.

Johnson rose to No. 1 in the world starting with the first of three straight victories, the first player to do that going into the Masters in more than 40 years. Two of those titles were World Golf Championships, and his undefeated week at the Match Play made him the first player to capture all four of the WGCs.

Johnson was at Augusta National on Wednesday to play nine holes before the first wave of storms moved in.

"I've got a lot of confidence in my game right now, especially with the way I've been playing the last few tournaments," he said Tuesday. "But, you know, anything can happen."

Johnson also missed the 2012 Masters, withdrawing two days before the start of the tournament, saying he had tweaked his back from pulling a jet ski out of the water. Golf.com cited an unnamed source two years later as saying Johnson had been suspended for a positive cocaine test. His management denied that he had been suspended.