During an eight-season pro playing career, which began in 1948, Keller appeared as a catcher in 25 MLBgames for the Washington Senators between 1949 and 1952. A left-handed batter, he stood 6 feet 1 inch (1.85 m) tall and weighed 200 pounds (91 kg). His 11 big-league hits included five doubles and one home run, a two-run shot hit at Fenway Park off James Atkins of the Boston Red Sox on September 29, 1950.[2]
After managing in the Senators' farm system during the late 1950s, he scouted for them until the franchise moved to Minneapolis–Saint Paul as the Minnesota Twins after the 1960 season. Keller, however, remained in Washington as farm system director of the expansion Senators in 1961 and 1962. After spending 1963 with his old organization, the Twins, as a scout, Keller rejoined the expansion Senators as their director of player development and scouting in 1964, a post he held for 15 years, through the team's 1972 transfer to Dallas–Fort Worth as the Texas Rangers.
Keller then served as the Mariners' vice president, baseball operations, and general manager from October 1983 to July 12, 1985, when he resigned. The Mariners went 115–132 (.466) during his 11⁄2-year term as general manager, while incorporating Langston, Swift, Alvin Davis and Jim Presley into their lineup. He later scouted for the Detroit Tigers and Anaheim Angels.