Look...I am not a sports fan, I'm more of a movie and television fan, but if I went up to one of the stars I liked, let's say Alexander Skarsgard, and he accused me of stalking him and beat the shit out of me, I'll be damned if I am going to let him roll around town happy as a clam because I don't want him to miss a movie/TV roll (though for the sake of all that I've heard of him, he would probably buy me a chicken burrito and some strawberry ice cream and skip the beating).
This is what happens in Big Fan. Patton Oswalt plays an immense sports fan whose life revolves around sports. He works as an attendant (kind of like in King of Queens) in a parking lot and maybe lives with his mother?
During a night out, he sees his favorite player going into a bar and he and his friend follow and eventually approach and ask for an autograph. The friend says they came all the way from Staten Island and the player starts accusing them of following him and beats the crap out of Patton in the middle of the bar. When he wakes up, battered and bruised in the hospital, the cops say the player could get 3-5 if he just goes over everything that happened. Well, he doesn't want to talk and instead has a fit that his brother is suing the player on his behalf. His mother calls him "sick".
This is a Patton Oswalt we are not familiar with and it looks good on him.