In a November 12 story in The Athletic, Fiers said the Astros had engaged in sign-stealing methods in 2017 that violated MLB's rules.
Fiers pitched for the Astros in 2017, the year Houston defeated the Los Angeles Dodgers to win the franchise's first World Series.
The Athletic's report with Fiers' on-the-record comments spurred MLB to launch its investigation, which found that the Astros illegally created a system that decoded and communicated the opposing teams' pitching signs to their own players.
On Tuesday, MLB commissioner Rob Manfred was asked if the league was concerned about Fiers' safety -- and, if so, what steps would be taken, particularly when the A's play in Houston this season.
When asked if he might consider returning his World Series ring, Fiers said he currently has no plans to do so unless it's mandated for the 2017 team to do that.