Dustin Johnson out of Masters

AUGUSTA, Ga. -- Dustin Johnson, the 12th-ranked player in the world, will miss the Masters because of a back injury, he tweeted on Tuesday.

"First 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," Johnson wrote.

The five-time PGA Tour winner underwent offseason knee surgery immediately after the Presidents Cup in November and got off to a slow start in 2012, although he tied for fourth at the Feb. 16-19 Northern Trust Open and was tied for ninth at the WGC-Accenture Match Play the week after.

His last tournament was the WGC-Cadillac Championship at Doral, where he tied for 35th on March 11.

His agent, David Winkle at Hambric Sports Management, said Johnson first had back pain in January when he withdrew from the Humana Challenge, and played through minor pain the next six weeks.

"His back bothered him from time to time. He kind of played through the pain, but it was never crippling," Winkle said in a voicemail. "He rested it at Bay Hill, got back to working some last week, and tweaked it last week lifting a jet ski."

Johnson, who was born in Columbia, S.C., and lives in South Florida, had been going through therapy and taking anti-inflammatory medicine. Winkle said he will be seeking opinions from other doctors and "hopefully, it's nothing serious."

"At the same time, it did knock him out this week," Winkle said. "Needless to say, he's pretty bummed out at this point."

Johnson has played in the Masters three times, finishing tied for 30th in 2009 and tied for 38th in both 2010 and 2011.

With Johnson's withdrawal, the Masters field is 96 players.

Information from The Associated Press was used in this report.