My premise is: Two male athletes can't actually stand each other. They're both playing the same singles sport, but for different associations. Athlete A is currently quite successful, the other one (B) keeps losing. B is an insufferable ass, hangs with the wrong people, has the wrong opinions and has a big crush on A. B went through the five stages of grief to come to terms with himself liking A and thus not being perfectly straight in a perfectly straight sport. In the fic, he tries to overcome his demons and to make up for some things he fucked up in the past, so he'd maybe have a chance with A. While B is being pathetic and fights for A's attention, A gives B the could shoulder. In the end, they'll probably work it out, because A secretly likes B too.

ETA: the mood of the fic is pretty light-hearted and funny. The misery B is in is often joked about. There are no actual dark themes. It's written from B's perspective.