The A's, already owners of four catchers on their roster at the time of the trade, added another in prospect Derek Norris. Depth at the position allowed them to make a move with the 29-year-old Powell.
"Landon's a guy that's been with us; we're certainly comfortable with him as a backup," A's general manager Billy Beane said of Powell, who has an excellent rapport with the pitching staff. "The hope is that he remains with us and is competing for the backup job again next year as he's done. Obviously, we'd like to hold on to him, but we'll see what happens."
Powell has appeared in 123 games over the past three years with Oakland and most recently played in just 36 contests as Kurt Suzuki's backup this season, batting .171 with one homer and four RBIs.
Miller, meanwhile, spent the majority of 2011 with Triple-A Sacramento, hitting .276 with 32 home runs and 88 RBIs in 110 games. As a September callup in Oakland, the outfielder went 3-for-12 with one homer and two RBIs in seven games and, by season's end, was expected to compete for a starting-outfield job come spring.
"He had a real good year for us at Triple-A," Beane said. "The hope is we can retain him in some way, shape or form once this process is over. He came on pretty good last year, and I'm sure others took notice as well."
Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.