Carter, who was best known for his role as the catcher on the 1986 World Series champion Mets, died Thursday following a lengthy battle with brain cancer.
Mills played parts of four seasons in the Major Leagues, all with the Expos from 1980-83. Carter played 12 of his 19 seasons in the Majors with the Expos (1974-84, 1992).
"My thoughts are with [his wife] Sandy and his family," Mills said. "We haven't seen him recently, but we got a Christmas card from the family this past Christmas. Our memories of him are back when he played and shortly after, which is how we'd like to have them. He's a special guy, has a special family. He was a good family man."
Carter and Mills played very different roles with the Expos, but Mills remembers him being down to earth. Carter was the starting catcher who was well en route to a Hall of Fame career, while Mills was a bench player who never played more than 54 games in any of his four seasons in Montreal.
"He got close to a lot of people simply because that's how he was," Mills said. "Our family and our wives became close. He wanted to be a good teammate, wanted to play on a winner and be a good player on any ballclub he was with. He did that with our ballclub in Montreal when we were one of the best teams in the NL, and he did the same thing with the Mets. He'll be missed."
Carter hit 324 home runs with the Expos, Mets, Giants and Dodgers, finishing his career back where he started, in Montreal in 1992. He entered the Hall of Fame in 2003 with an Expos cap, on a plaque referring to his "signature smile" and clutch hitting.
His No. 8 was retired by the Expos in 2003.