Hello, there's something good in you logline.
I think it's the possibilty of a inner jurney for the main character, the monomaniac?fan who must learn the true beauty of sport.
Besides, I can't see what there will be actually in the movie... I think this is a very hard concept to exploit.
The concept reminds me of?Brewster's Millions, where Richar Pryor's fantastic inheritance is linked to perverse obligation to spend?30 millions in 30 days, and he buys the shitty local baseball team with the idea of loosing money but... the team is doing better than he thought.
One suggestion, maybe the uncle is not an unknown uncle but a hated uncle who was a supporter of the team that the main character hates. And he was also a very rich gready uncle. Maybe the story take place in a town with two competing teams (it's where the hate grows better).
You should mention what sport it is.