"Arena" by Fredric Brown was adapted (sort of) twice for TV...
...first, in 1964, on the Outer Limits as "Fun and Games", starring Nick Adams.
You'll note a number of differences between the story and the episode, including a pair of new characters, a mate for the alien, and a woman with a hidden past who works with the hero!
A year later the story was reused, on Classic Star Trek as "Arena"...
...except it wasn't...exactly.
Gene Roddenberry's right hand man, producer Gene Coon, had submitted a story about Capt. Kirk fighting an alien starship commander to see whose ship would survive.
When the story was fact-checked, it was discovered that Coon had inadvertantly used numerous elements from Brown's story, which Gene had probably read years earlier!