Armas and a player to be named later (Jim Mecir), were traded to the Boston Red Sox in 1997 for Mike Stanley and Randy Brown.

[1] Various injuries held him back until 2003, when he was the team's Opening Day starter, shutting down the Atlanta Braves at Turner Field, 10–2.

But the strong start turned into a breakdown weeks later, after he was diagnosed with injuries in his arm and shoulder which required season-ending surgery.

At that time, Armas had a record of 2–1, 23 strikeouts and a 2.61 ERA, with a WHIP of 1.065 and not allowing a home run until his fifth and last start.

[3] Armas missed one month with arm problems, but in his second game back from the disabled list he pitched seven innings, allowing only one run on three hits.