[2] He subsequently signed a professional contract with the New York Rangers in 1964, but only played 29 games with this club over the next three years, spending most of his time with the minor league Baltimore Clippers.

[4] Plager was reunited with his brothers Bill and Barclay as all three took the ice for St. Louis Blues as the team started its existence with a hard-hitting, defensive-oriented squad that appeared in three straight Stanley Cup Finals.

In his one-season behind the bench, he led the team to a Turner Cup championship and won the Commissioners' Trophy as coach of the year.

During the 1992–93 season, he became the Blues' head coach, but, unhappy with his new role, he resigned after 11 games to return to his job as vice president of player development.

[12][13] Plager died of a "cardiac event" suffered while driving eastbound on Interstate 64, on March 24, 2021, leading to a two-vehicle collision.