Ex-Mets shortstop Eddie Keenan (.342 in the team's second consecutive pennant-winning season) becomes Warrior Iddikinnin, drafted by Earth and dispatched across the galaxy to civilize the feudal economy of the planet Melon. "Allen Kim Lang has produced a hilarious blend of baseball, exobiology, ethnology, and pure fun in this glorious, slam-bang adventure, the story of baseball's introduction to an alien planet."
I read this a very long time ago and it stuck in my head, sadly not the title or author but the plot. I am deeply grateful to a librarian at the Library of Congress who helped me find the name of this novel which is fun yet serious and thoughtful.
Abebooks has this in stock although I couldn't find anything at Archive.org or Thriftbooks. The odd thing is our public library had this in hardback back in the 1960s so it ought to have been modestly popular.