Sievers was signed by the St. Louis Browns as a free agent in 1947. Sievers debuted in the major leagues on April 21, 1949. He played in Major League Baseball as a first baseman/left fielder. From through , Sievers played for the St. Louis Browns (1949–53), the original Washington Senators (1954–59), Chicago White Sox (1960–61), Philadelphia Phillies (1962–64), and finally the new Senators (1964–65). He batted and threw right-handed.