NEW YORK -- Randy Johnson underwent surgery to repair a herniated disk in his lower back on Thursday, fixing a problem that plagued him over the season's final month and into the playoffs.
The operation was performed in Los Angeles by back specialist Dr. Robert Watkins, who did the same surgery on Johnson in September 1996.
Barry Meister, Johnson's agent, said that Johnson is expected to be ready to pitch by Spring Training and should be fine by Opening Day.
"Everything went fine," Meister said. "The doctor was pleased. It went just as expected."
General manager Brian Cashman recently said that Johnson, 43, could be ready for Opening Day 2007, but added that it wasn't a sure thing.
"He's going to be behind in Spring Training," Cashman said last week. "The time frame would permit him to be ready by Opening Day, but because of his age, I don't think it would be a fair assessment to guarantee it."
Johnson is expected to return to his home in Phoenix on Friday, according to Meister.
Johnson went 17-11 this season with a 5.00 ERA, but he was hit for five runs in 5 2/3 innings in his Game 3 start of the American League Division Series against the Tigers.
The 43-year-old left-hander, who is 20 victories shy of 300 for his career, has one year and $16 million remaining on his contract.
Mark Feinsand is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.