This strip originally ran in 1959. That’s two years before the Senators moved to Minnesota and became the Twins, so the reference is to the Minneapolis Millers of the minor-league American Association.
In 1959, the Yankees finished in third place in the American League, and the Millers finished in first place in the AA (but lost the Junior World Series to the Havana Sugar Kings of the International League). They probably could have taken the Yankees.