In seven seasons with the A's he hit .321 with 48 home runs, 612 RBIs and 88 triples in 866 games played.
Baker played third base for the Athletics until 1915, when he sat out the entire season in a contract dispute with Connie Mack. He remained in baseball, playing for Upland, Pennsylvania in the semiprofessional Delaware County League.
Mack sold Baker's contract in 1916 to the New York Yankees, with whom he finished his career. He led the league with 141 games played in 1919.
Baker retired for one season in 1920, but came back to play two more years with the Yankees (and in their first two World Series as well), finishing as a Yankee with a .288 batting average, 48 home runs and 375 RBIs in 676 games.
^"Baker, Frank". National Baseball Hall of Fame and Museum. Retrieved September 26, 2012.
^Lanctot, Neil (1994). Fair Dealing and Clean Playing: the Hilldale Club and the development of black professional baseball, 1910-1932. Jefferson, NC: McFarland. p. 11. ISBN0-89950-988-6.
"Semiprofessional" may be a euphemism. Upland employed other major leaguers between 1915 and 1919 (including Baker's longtime teammate Chief Bender), and by 1919 the Delaware County League was declared an outlaw league by organized baseball.