“I’m in this for the long haul, and I want to finish this up,” Nationals Manager Davey Johnson told players on the final day of the season. (John McDonnell/The Washington Post)

On the final day of the 2011 season, as the Washington Nationals prepared to put the final touch on one of the franchise’s best months, Davey Johnson called players into his office one by one. The Nationals had guaranteed a third-place finish and improved by 10 victories over the previous year. For Johnson, the progress represented a signpost, not an end point. He wanted his players to know.

“I’m in this for the long haul, and I want to finish this up,” Johnson told them. “I don’t want to come in here for a year. I want to stick around.”

Monday morning, the Nationals officially named Johnson their manager for the 2012 season, exercising an option in his contract and continuing a tenure that began last season amid upheaval and led to perhaps the most promising stretch since baseball returned to Washington.

General Manager Mike Rizzo called bringing Johnson back, a move long expected, an “easy decision.” Players uniformly supported the return of Johnson, 68, who will be the oldest manager in baseball.

“It really feels great,” Johnson said. “It’s such a great organization, such a great bunch of kids. We didn’t come close to the ceiling this year. I really feel like I’m kind of their father figure. I think they respect me, and I feel like I’m the guy to steer them along their path.”

Johnson moved from a front-office role to the dugout last season on June 27, four days after Jim Riggleman’s abrupt resignation. He went 40-43, including a 14-4 finishing kick that built uncommonly high expectations for 2012. He gained the trust and support of players, most of whom had met Johnson while he worked in his front-office position.

“If you have someone struggling, he’s going to stick with him,” third baseman Ryan Zimmerman said. “He puts the lineup up every day, and that’s going to be the lineup. We respect him for giving us our space, and because of that we’re going to play hard for him.”

Rizzo interviewed multiple candidates to become the Nationals’ manager in 2012, including third base coach Bo Porter. But there was never a question who would remain in charge. Rizzo feels a distinct comfort with Johnson, whom he hired as a special assistant the day he became the Nationals’ interim general manager in 2009.

This June, when Riggleman suddenly quit, Rizzo thought first of Johnson, who had last managed in the majors in 2000 for the Los Angeles Dodgers. On the night of June 23, after Riggleman resigned, Rizzo had dinner with Johnson at a Washington hotel.

“The only question I had about Davey taking over was, did he want to do it?” Rizzo said. “Was his energy level and his focus going to be there?”

And so, the basis of Johnson’s appointment for 2012 arrived well before the opportunity arose, all the way back in last spring training. Johnson arrived last February with more energy than he had felt in years, largely because of an ablation doctors at the Mayo Clinic performed on his heart over the winter. He pounded groundballs and moved briskly from field to field.

“He had an energy about him,” Rizzo said. “I thought to myself, ‘Davey is really into it and really fired up for the season.’ ”

Johnson, who turns 69 in January, will be the oldest manager in the major leagues. He’s a year older than Tony La Russa, who announced his retirement Monday, three days after his St. Louis Cardinals won the World Series. Age, though, does not seem to be an issue for Johnson, even after a series of health scares.

“He seems younger to me now than he did with the Dodgers,” his wife, Susan Johnson, said in September.

Johnson, the third Nationals manager to begin a season in the past four seasons, provides a measure of stability. Johnson will bring back his full coaching staff aside from bench coach Pat Corrales, who will remain with the Nationals as a trusted player development adviser. Whether Johnson returns in 2013 remains undecided, but the Nationals have at least assembled a stable collection of coaches and an unquestioned voice.

“We’ve never really had a consistent kind of leader or manager,” Zimmerman said. “There’s always been shuffling going on, change from year to year. I’m hoping we can get into having the same group of coaches for a period of time. That consistency helps.”

Said closer Drew Storen: “It’s nice to know that with the way we were playing at the end of last year, we’re going to be able to build on that instead of having to start over at square one.”

Johnson wasted no time ratcheting up the expectations for his team. Asked how far the Nationals could go next season, Johnson responded with a high ambition for a franchise that has not had a winning record since relocating to Washington in 2005.

“Winning the pennant. Winning the National League,” Johnson said. “I couldn’t have said that last spring. I didn’t think the talent was ready. After being there and seeing the progress that some young players made, I think we definitely can contend. I would be sorely disappointed if we didn’t do just that.”

Having managed 2,121 games during 15 years as a major league manager, Johnson has a .561 winning percentage with five teams. His greatest triumph came in 1986, when his 108-win New York Mets won the World Series. Johnson’s experience and mutual trust with Rizzo will allow him to operate with an autonomy other Nationals managers have lacked.

“He’s won as a player. He’s won as a manager,” Zimmerman said. “He’s very calming. There’s no panic in him. He has enough self-confidence that he’s going to do what he wants to do, no matter what the front office thinks, what the fans think. Not to say he rebels against the front office, but he has the [stature] to be able to do some things other guys might not be able to do, take some risks that some other people wouldn’t.”

The Nationals, like this offseason, will hold an option for the 2013 season of Johnson’s contract. They can either make him the manager for that season, too, or they can make him an influential front office consultant. Johnson, keeping to his personal mantra, has not considered his long-term status.

“I look at things today with an eye on tomorrow,” Johnson said. “My wife is the one who thinks about what we’re doing two weeks from now.

“I really like where I’m at in my life. Managing the Nationals this year was a lot of fun for me. It’s serious business, but I love the game of baseball. I love the way we came along and we progressed as a team. That was fun for me.”