For WEEI talk-show host John Dennis, “rock bottom” took place during the Red Sox’ home opener against the Washington Nationals Monday afternoon at Fenway Park.

He says all he had was one drink. Whatever the number, it was enough to convince Dennis, who hosts the popular “Dennis & Callahan” morning-drive program with Gerry Callahan and Kirk Minihane, to check himself into rehab.

“I knew immediately that one (drink) was not going to be enough,” Dennis said during a telephone interview yesterday after informing station management of his decision. “I can stop for long periods of time, but then once I have one, one seems like a good idea, and then two seems like a really good idea. And then four seems like a great idea.”

By his own count, Dennis said he had gone 40 days without touching alcohol. But then came the traditional home opener, after which he decided to take a leave of absence from WEEI.

“They’re not sending me to the Betty Ford in California,” Dennis said. “It’ll be local. But it will be inpatient, and I’m told it’s approximately four to five weeks. Could be a little more or a little less.”

A statement emailed to me by Dennis includes the following: “I’ve made the decision to take serious steps to eliminate the role alcohol plays in my life before it impacts my health. I’m told it’s an arduous undertaking, but it’s one I’m willing to embrace. I know it can be a lifelong battle, but it’s one I want to fight.”

JOHN DENNIS' STATEMENT: WEEI host in his own words

During the telephone conversation yesterday, Dennis was more blunt.

“It’s time to grow up,” he said. “It’s time to be a better husband to Kathy. It’s time to be a better dad to my two daughters, and a better grandparent. And you know? A better teammate to Kirk and Gerry.”

According to Dennis, he was assured his job will be waiting for him when he returns. Station manager Phil Zachary confirmed that last night.

“Absolutely,” Zachary said. “Not a question at all. WEEI has been built on the ‘Dennis & Callahan Show’ with Dennis and Callahan and Kirk Minihane, and we don’t see a future without John Dennis.”

For Zachary, Dennis’ disclosure did not come out of the blue.

“He and I have been talking about a problem he’s had with alcohol for a while,” Zachary said.

Minihane, a self-professed recovering substance abuser who says he hasn’t had a drink since 2012, likened Dennis to a character from the hit TV series “Mad Men.”

“The way he looks, the way his hair is, the way he talks, the way he dresses, some of the words he says, I feel like you could put John in ‘Mad Men,’ like Season 2, and he’d be the most successful advertising man in the history of ‘Mad Men,’ ” Minihane said. “I think John has that 1960s mentality still about (alcoholism), where he thinks he should be embarrassed about it. He absolutely should not be.”

Dennis, 63, had been a sports anchor for 22 years at WHDH-TV, leaving the station in 1999 to team up with Callahan, a former Herald columnist and Sports Illustrated staffer, to host a mid-morning program at WEEI. Three years later, the show was moved to morning drive and became a ratings giant for the station. Minihane became a permanent addition to the show in February 2013.

“I’m getting up there,” Dennis said. “I want to live a long and happy life. I want to be a snow bird, between Miromar Lakes (Fla.) and Boston, and I want to get things straightened out before anything happens to me health-wise. I just had my physical and everything is fine, but it was one of those things where back in the day, having a couple of drinks was for an event, like a birthday party, or an opening or some kind. Or watching the Super Bowl. But my events became more frequent.

“It was an accumulation of years of watching ballgames, watching on TV, and out-to-dinner type things. That seemed to increase the last year or so.”

To compound matters, Dennis must arise at a time of day when the vast majority of his listeners are still asleep.

“I was really careful for a long time not to (drink) on school nights, because a 3:45 a.m. wakeup call is brutal,” Dennis said. “And by and large I have lived by that rule. But I will admit there have been some Mondays when I’d walk in and I was a little fuzzy, and I don’t think at my best.

“I don’t drive drunk. I didn’t run over anybody. I didn’t fall down and crack my head. I didn’t get in a fight. None of that stuff. It was an accumulation of more frequent events where I said, ‘Oh, yeah, it would be a good idea to have a cocktail while I’m watching this game.’ And I wanted that to stop.”