Starffin was signed by the Tōkyō Kyojingun (now the Yomiuri Giants), outside the draft, in 1936, and played for them until 1944. He was one of the premier pitchers in the Japanese baseball "dead-ball era" (pre-1945), when many of Japan's best players were serving in the Imperial Japanese Army. He won two MVP awards and a Best Nine award, and won at least 26 games in six different years, winning a league record 42 games in 1939. He followed his record setting 1939 performance with another 38 wins in 1940. He returned to professional baseball in 1946, but chose not to return to the Giants, instead signing a contract with a new team, the Pacific (an offshoot of the team now known as the Yokohama BayStars). Starffin also played for the Shochiku Robins (now the Yokohama BayStars) in 1947, Kinsei/Daiei Stars (now the Chiba Lotte Marines) after 1948, and finally signed with the Takahashi/Tombow Unions (an offshoot of today's Chiba Lotte Marines) in 1954-55. In 1955, his last season, he became the first career 300-game winner in Japanese professional baseball. He retired in 1955 with a career record of 303 wins and 176 losses.