UPDATE No. 5 (April 6, 2:03 p.m. ET):

Dustin Johnson is a WD from the Masters, as he walked off a practice green at his 2:03 p.m. ET tee time.

UPDATE No. 4 (April 6, 1:18 p.m. ET):

Dustin Johnson’s first range session is over. It wasn’t very long and all limited swings. He’s now back on the range, but his Masters status is still uncertain.

UPDATE No. 3 (April 6, 1:00 p.m. ET):

Dustin Johnson is on the range as we speak. We have to imagine now that Johnson will play!

UPDATE No. 2 (April 6, 12:37 p.m. ET):

It appears Dustin is indeed on the course now. A great sign!

#Breaking: Dustin Johnson is on the grounds, expected to play. He tees off at 2:03 p.m. #themasters pic.twitter.com/ZrsGmiJFjJ — Augusta.com (@AUG_Masters) April 6, 2017

UPDATE No. 1 (April 6, 12:01 p.m. ET):

Per Golf Channel’s Todd Lewis, Dustin Johnson will arrive at Augusta National roughly around 1 p.m. to practice and is “cautiously optimistic” about playing.

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AUGUSTA, Ga. — Masters favorite Dustin Johnson is on the clock, facing a 2:03 p.m. Thursday tee time at Augusta National after a serious fall injured his lower back Wednesday afternoon.

It remains uncertain if Johnson, the top-ranked player in the world, will be able to play this weekend.

“At roughly 3 p.m. today, Dustin took a serious fall on a staircase in his Augusta rental home,” said Johnson’s manager, David Winkle of Hambric Sports, in a statement. “He landed very hard on his lower back and is now resting, although quite uncomfortably. He has been advised to remain immobile and begin a regiment of anti-inflammatory medication and icing with the hope of being able to play.”

More details of the random nature of the slip and fall emerged Wednesday evening.

“There were three small wooden steps, and he had some socks on, it was slippery and he slipped,” Johnson’s trainer, Joey Diovisalvi told Masters Radio on Sirius-XM. “He landed on the left side of his lower back in the muscular area,” Diovisalvi added. “You know these things happen … but the good news is it wasn’t something that was a flight of stairs.”

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What will help Johnson is that he is in the last group for the opening round, with two-time Masters champion Bubba Watson and PGA champion Jimmy Walker.

“We’re optimistic,”Diovisalvi added. “We have to see what happens overnight.”

On the flip side, strong winds are in the forecast. Those could pose an additional challenge for anyone with an ailing back. Back problems have already claimed the game’s biggest name in this event: Tiger Woods.

Johnson did cancel a scheduled at Golf Writers Association of America’s annual dinner Wednesday evening, where he was scheduled to receive the group’s player of the year award.

Johnson was the betting favorite to win this year’s Masters, listed at 17-2 by VegasInsiders.com.

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

On Tuesday, Winkle described Johnson as being “in as good a shape as I’ve ever seen him in every aspect of his game and his life.”

Johnson has won three straight tournaments — including a pair of World Golf Championships — heading into the Masters.

Two years ago, Rory McIlroy ruptured ligaments in his ankle a few weeks before he was to defend his title in the 2015 British Open when he was No. 1 in the world.

But this was different.

Johnson was at Augusta National Wednesday to play nine holes before the first wave of storms moved in. He was a strong favorite to become the first player since Woods in 2002 to win the Masters at No. 1 in the world.

The Associated Press contributed to this report.