After his playing career, Miller coached and instructed for 28 seasons (19 in the St. Louis Cardinals organization), mainly in the minor leagues.

In spite of impressive showing, manager Earl Weaver informed him the Orioles had assigned him to start the season at Rochester.

However, Weaver was empathetic, later admitting to a Sporting News reporter that he "felt sorry for the guy" and that "he had earned the chance to pitch in the big leagues."

[2] The Orioles finally called Miller up later that season and he made his MLB debut on June 9 against the Oakland Athletics, just two weeks after turning age 29.

In Miller's seven Major League seasons, he pitched 465+1⁄3 innings in 251 total games, making one start, and compiling a 3.23 ERA with 22 saves.

After his release from the Mets, Miller pitched three more years in the Cardinals organization with the Louisville Redbirds, where 1984 was his final season as a player.

In 1985, Miller was named as pitching coach with the Cardinals' Class AA minor league club, the Arkansas Travelers, where Jim Riggleman was the manager.

Fregosi left during the season to replace Tony La Russa as manager of the Chicago White Sox.

The White Sox fired Fregosi following the 1988 season, and Miller took coaching roles in the Detroit Tigers (1989–1990) and Cleveland Indians (1991–1994) systems.

No reason was directly given, although general manager John Mozeliak commented, "Just from a standpoint of when we were putting the coaching staff together last year, we were doing it quickly and Dyar deserved that opportunity.