A's pitcher Sean Manaea rips the Astros for how they have handled their role in the sign-stealing scandal. (0:42)

The Oakland Athletics filed a formal complaint to Major League Baseball about the Houston Astros' sign stealing before Mike Fiers told The Athletic about the scheme, manager Bob Melvin and general manager David Forst told the San Francisco Chronicle.

"MLB does a great job of monitoring these things, but it's very difficult if a team calls in and complains about something, they can only do so much," Melvin told the newspaper. "It took a player and a player who was on that team to put it over the top. And I think MLB is handling it very well right now."

Fiers, who now pitches for the A's, made it clear he is moving forward after he told The Athletic in November that his former Houston team had stolen signs using a video camera in center field during the Astros' 2017 run to the World Series title.

"Right now I want to focus on this team and not the past," said Fiers, who has declined to speak in detail about the scheme or his decision to go public.

The revelations prompted an investigation that shook up several teams. Houston manager AJ Hinch and general manager Jeff Luhnow were fired on the same day they were suspended by commissioner Rob Manfred. Former Astros bench coach and then-Boston Red Sox manager Alex Cora also was dismissed, and then ex-Astros player Carlos Beltran lost his job as New York Mets manager.

"I'm glad we're at this point right now, and obviously Mike had a lot to do with that," Melvin told reporters Wednesday as pitchers and catchers held their first spring workout. "The game's better for it from this point going forward. I think it's all about moving past right now and getting through a lot of the issues that you saw. It's supposed to be an equal playing field, and it wasn't."

The Associated Press contributed to this report.