"Davey's a perfect fit for this job at this particular time. He's a guy with a track record that's beyond reproach. He knows the system, he knows the staff, he knows the major league club and he's a terrific baseball guy and a proved winning manager," general manager Mike Rizzo said.
Interim manager John McLaren ran the team for the third straight game in Sunday's series finale against the Chicago White Sox. Riggleman's former bench coach will leave the team after the game and be reassigned to scouting duties within the organization.
Less than an hour before game time Sunday, a loud round of applause could be heard coming from the Nationals' clubhouse as Rizzo thanked McLaren. At the same meeting, Rizzo informed the team of Johnson's hiring - not a well-kept secret over the last three days.
"It's an extremely positive reaction. They all know Davey, he's been in spring training, in uniform," Rizzo said. "They've interacted with him, they know his resumé and just talking to him, the respect that he has in that room, even before he sets foot in there as manager, is second to none."
Johnson was not available for comment Sunday and would not be returning calls, a team spokesman said. He was scheduled to join the team later for the flight to Los Angeles.
The 68-year-old Johnson managed the Mets, Dodgers, Reds, and Orioles over 14 seasons and compiled a 1148-888 record. He led the 1986 Mets to a World Series championship, and 11 of his teams finished first or second 14 times.
He played for the Orioles, Braves, Phillies, and Cubs in a career lasting from 1965 through 1978. He played a total of 122 games for the Phillies in 1977 and 1978 - a season when he set a major league record with two pinch-hit grand slams.
Even though he hasn't managed in the majors for 11 years, Johnson did skipper Team USA in the 2009 World Baseball Classic, the 2008 Olympic team in Beijing, and two summers ago managed amateur players in a Florida summer collegiate league.
Rizzo said he talked with several other people about the job but did not formally interview them because Johnson was easily his first choice after Riggleman bolted.
"When we got the news, you automatically go into 'Plan B' mode and try to think outside the box," Rizzo said. "We had to make decisions rationally and clearly, but quickly. We were fortunate to have such a clear-cut and easy alternative right there."
Riggleman resigned abruptly Thursday after the Nationals beat Seattle, unhappy that Rizzo declined to have a conversation about picking up his option for 2012. The departure was stunning for its timing - the Nationals have won 13 of their last 15 games.