World number one Dustin Johnson is a doubt for the Masters after suffering a "serious fall" the day before the tournament begins.
Johnson is the pre-tournament favourite to be presented with the green jacket for the first time after winning three consecutive events before heading to Augusta.
However, it remains to be seen if the U.S. Open champion will play in the first major of the year following an accident at his rental home on Wednesday.
A statement released by the American's manager David Winkle said: "At roughly 3pm today, Dustin took a serious fall on a staircase in his Augusta rental home.
"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 regimen of anti-inflammatory medication and icing, with the hope of being able to play tomorrow.
"I will refrain from commenting further until I know more about Dustin's condition."
Johnson, who finished in a tie for fourth at the event last year, took over at the top of the rankings in February and has remained there following some outstanding performances.
He is due to tee off with Bubba Watson and Jimmy Walker at 2:03pm (local time) in the final group of the day.