NASHVILLE, Tenn. (AP)  — Bobby Johnson said Wednesday that there’s never a good time for a football coach to quit — as he retired less than a month before Vanderbilt starts fall practice.

The 59-year-old Johnson said it was a very difficult decision, one that he began seriously considering month ago. He said he informed vice chancellor David Williams in a meeting Monday. The announcement came Wednesday after Williams couldn’t talk Johnson out of retiring even with offering more money.

“Football is not life, but it’s a way of life and it consumes your life,” Johnson said. “You only have so many years to live, and you want to see a different way.”

During the 35-minute news conference and in follow-up interviews, Johnson never said why he chose now to retire. He did say neither he nor his wife have any health concerns.

The timing of his retirement could not come at worse time for Vanderbilt.

Johnson was scheduled to appear at next week’s Southeastern Conference’s preseason media days, the annual kickoff to the new season. It’s just about three weeks before the Commodores start fall practice and seven weeks before the Commodores’ opener Sept. 4 against Northwestern.

Coaching college football is demanding, and Johnson indicated he wasn’t ready to continue giving 100 percent.

“If you don’t have the investment in a season where it means everything to you, then I don’t think you should be coaching,” Johnson said.

News leaked out Wednesday morning with WGFX-FM 104.5 The Zone citing sources that Johnson was resigning. That came four hours before Vanderbilt officials planned to inform the Commodores themselves, so the news conference was hastily scheduled with assistant head coach Robbie Caldwell named the interim head coach.

Coaches left reporters to speak with players who already had heard the news from friends or text messages. Once Johnson spoke to them, they reacted with stunned silence. Then the Commodores immediately went to a scheduled workout.

“This isn’t something you can sit around and mope about,” defensive lineman T.J. Greenstone said. “Having coach Caldwell helps a lot. He knows the kind of people we have here. He knows how the system works. He knows the personnel. We’re not planning on missing a beat here.”

Defensive lineman Adam Smotherman, a Tennessee native, credited Johnson with changing Vanderbilt from a favorite homecoming opponent to a program with a chance to win every game.

“I hope he is happy and finds I guess the happiness that he’s looking for out of life. We’re going to move on. We are Vanderbilt football. We’re going to keep going and keep trucking,” Smotherman said.

Williams said he realized Johnson was serious when he called the coach’s house late Tuesday night and spoke with Catherine Johnson.

“I could tell from her voice I had lost,” Williams said.

Caldwell will be given the chance to keep the job with his performance this season. Williams said he has a coach right now and has no plans for a national search.

“I’m not searching for anything other than a victory and a lot of them,” Williams said.

Johnson started coaching in 1976 at Furman and finishes with an 89-102 record overall. He led Vanderbilt the past eight seasons and went 29-66, coaching the Commodores to their only non-losing season since 1982 in 2008 with a win at the Music City Bowl that gave them a 7-6 record. He went 2-10 in 2009.

“This is quite a shock to us,” said Caldwell, who learned of Johnson’s decision Wednesday.

Caldwell has never been a head coach before outside of a stint as a high school baseball coach for one season in South Carolina. He didn’t even have time to alert his family with the news and had to quickly change from shorts to pants for the news conference.

As Caldwell answered questions about whether he was ready to be head coach, Johnson interrupted.

“He’s ready,” Johnson said with a smile.

Johnson had become just the third coach in Vanderbilt history to hold the job for at least eight years, joining Dan McGugin and Art Guepe. Johnson went 29-66 at Vanderbilt and coached the Commodores to their only non-losing season since 1982 in 2008 by winning the Music City Bowl.

That was only Vanderbilt’s second bowl win ever and first since the 1953 Williams had that trophy brought out and put on a table during the news conference.

Johnson also ended losing skids to eight other SEC teams during his tenure, including a 22-game string to Tennessee in 2005.

“They expect to win,” Johnson said of the Commodores. “That’s the best thing I could’ve done for this program.”

But he lost the top recruit of his incoming class in February when Georgia running back Rajaan Bennett, the highest-rated player ever signed to Vanderbilt, was shot to death at his home. Asked about competing in the SEC as the league’s only private school, he cited a stat that Vanderbilt had lost 26 games by seven points or less during his tenure.

“That’s kind of tough,” Johnson said.