By Simon Evans
AUGUSTA, Georgia (Reuters) - World number 12 Dustin Johnson has withdrawn from this week's U.S. Masters due to a back injury, the American said on Tuesday.
"I have to apologize to the fans and sponsors. With heartfelt regret, I won't be playing in the Masters due to a tweaked back," he said on Twitter.
Johnson will not be replaced in the field for the first major of the season.