Robert Frank Knoop is an American former Major League Baseball second baseman and coach. In his nine-year MLB career, he appeared in 1,153 games as a member of the Los Angeles / California Angels (1964–69), Chicago White Sox (1969–70) and Kansas City Royals (1971–72). He threw and batted right-handed, stood 6 feet 1 inch (1.85 m) tall and weighed 170 pounds (77 kg).

In baseball and softball, second baseman, abbreviated 2B, is a fielding position in the infield, between second and first base. The second baseman often possesses quick hands and feet, needs the ability to get rid of the ball quickly, and must be able to make the pivot on a double play. In addition, second basemen are usually right-handed; only four left-handed throwing players have ever played second base in Major League Baseball since 1950. In the numbering system used to record defensive plays, the second baseman is assigned the number 4.