“Rule 18,” a 1938 Earth-Mars football story by Clifford D. Simak

Originally published in the July 1938 issue of Astounding Science Fiction magazine, “Rule 18” was the first short story author Clifford D. Simak wrote for editor John W. Campbell. Set in the year 2479, the story's plot revolves around the annual Earth-Mars football game, in which Earth’s coach cheats by using a time tunnel to recruit players from the past. According to When the Fires Burn High and the Wind Is from the North: The Pastoral Science Fiction of Clifford D. Simak (2006), by Robert J. Ewald:

“Rule 18” did not make very much impact on the readers, except for its influence on an eighteen-year-old fan and budding writer named Isaac Asimov. Asimov, in a letter to Brass Tacks, gave “Rule 18” a very low rating for its “incoherent” style. He received a letter from Simak asking for details so that Simak could profit from Asimov’s criticism. Asimov, on a closer rereading, found nothing wrong except for Simak’s technique of writing the story in separate scenes without explicit transitional passages. He wrote Simak to explain and apologize, then adopted the same device in his own stories. He also made use of what he called Simak’s “cool, unadorned style," and later credited Simak with being the major influence on his style.

According to the Internet Speculative Fiction Database, Simak's "Rule 18" has never been reprinted.