Randy Johnson has a herniated disk in his surgically repaired back, making the timing of his return to the Diamondbacks' rotation unclear. The 43-year-old Johnson seemed upbeat after the club revealed the diagnosis Tuesday, one day after Johnson visited with Dr. Robert Watkins in Los Angeles. Johnson went on the 15-day disabled list June 11 with a tight glute. "I won't back away," said Johnson, who also had a back operation 11 years ago. "I'm eager to still pitch. I've tackled this twice before."