The Red Sox also notified right-handed pitcher Sammy Stewart and infielder Dave Stapleton that they will not be offered contracts for 1987.
Seaver, who turns 42 on Nov. 17, injured his right knee in September and was unable to pitch in the playoffs or World Series. The right-hander underwent arthroscopic surgery last week.
Seaver has a lifetime record of 311-205 and a 2.86 earned-run average. He was 5-7 with a 3.80 ERA for the Red Sox in 1986, after being acquired from the Chicago White Sox in a June trade for outfielder Steve Lyons. Seaver also played previously for the New York Mets and Cincinnati Reds.
Armas, 33, was bothered by leg injuries for much of the past two seasons. Playing in 121 games in 1986, he hit .264 with 11 home runs and 58 runs batted in. In 1984, he led the major leagues with 43 home runs and 123 RBIs.
Stewart, 32, was 4-1 with a 4.38 ERA in 27 relief appearances this season, but he was injured May 31 and made only three appearances before August. He did not pitch in the postseason.
Stapleton, 32, hit .128 in 39 games this season, his seventh in the major leagues.