Well, to write a good fictional sports story, you need a great setting. Maybe a small town with a big sports dream or a big city with intense competition. Also, throw in some unexpected turns and keep the reader guessing. And don't forget about the emotional connection between the characters and the sport they love.
Start with a unique concept. Come up with a sport that's not too common or give a fresh twist to a familiar one. Also, create engaging characters with clear goals and motivations.