one-dimensional player (1974)

“Occasionally Carew is amused by the fact that he customarily is looked upon as a one-dimensional ballplayer, a player who can only hit and do nothing else. ‘I can run, throw, and field as well as many ballplayers in the big leagues, but people never want to talk to me about that,’ he said. ‘All they want to talk to me about is my hitting.’ Five hundred other big leaguers wish they had the same problem.” Milton Richman, United Press International, “Today’s Sports Parade,” News journal (Murfreesboro, TN), March 22, 1974, p8
NOTE: The term was used earlier in basketball and football.

No earliest use given in 2009 Dickson Baseball Dictionary