baseball player; ballplayer
Refers to a person who plays baseball, typically professionally or as a serious amateur.
He wants to become a professional baseball player.
That baseball player hits a lot of home runs.
野球 means 'baseball' (the sport), while 野球選手 specifically refers to a person who plays baseball.
選手 is a general term for 'player' or 'athlete' in any sport; 野球選手 narrows it to baseball.
Compound of 野球 (baseball) and 選手 (player, athlete).