Bench coach Pat Corrales, base coaches Tim Tolman and Jerry Morales, bullpen coach Rick Aponte and hitting coach Lenny Harris were all told before Sunday's 8-3 loss at Philadelphia they would not return.
Only pitching coach Randy St. Claire kept his job.
The Nationals went 59-102, 32½ games behind the NL East champion Phillies.
"I feel bad about losing every one of them," Acta said. "Those guys handled it a lot better than I did. They tried to pump me up. They are true professionals.
Strength and conditioning coach Kazuhiko Tomooka also will not return in 2009. General manager Jim Bowden declined to discuss specifics of the decision, only that it was simply time for a change.
"There are a lot of changes we need to make to get to where we want to get to," Bowden said. "We're going to start on 2009 [Monday] morning."
The Nationals hit only .251 as team, scored 641 runs and hit only 117 homers this season.
St. Claire became the Montreal Expos' pitching coach in 2003 and is the longest-tenured member of Washington's coaching staff.
"We thought he did a very good job with our young pitchers," Bowden said. "They continued to improve and get better."
Bowden said the fired coaches would possibly be considered for other jobs in the organization.
Acta seemed safe to return for his third season managing the Nationals.
"I feel good, confident in my own skin," he said. "I'll always have a job in this game. I'll be in the game the rest of my life."
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