Why is she calling him a loser?

People today take things too literally. Billy has a close relationship with his daughter and this was / is an inside joke between them. She said in her intro "I rewrote this song for you"...."I hope you like it and don't let anyone else see it".... My only thought is the directors missed an opportunity or maybe created one, by not cutting to him in the end and having him burst into laughter when the song got to that point.

Most reviewers are referring to it as something akin to a "loving, teasing tweak." Here's a take from a reviewer at Baseball Nation:

In professional sports, there's no epithet worse than loser ... but of course, in this context -- the context of a loving relationship within a movie that's less about winning than thinking -- it's not an epithet at all. It's a term of endearment, a message of love from a daughter to her father and also from the filmmakers to us ... It doesn't matter if the A's didn't win the World Series. It didn't matter if Billy Beane was, and still is, a "loser" according to the traditional standard. He's a winner because he fought the good fight and because his daughter loves him enough to sing him a song, and tease him.

This review compares the movie to the book, with nods to the movie humanizing Billy Beane in a way the book did not. I have read the screenplay for the movie, and it doesn't end the way the movie does, which is interesting.

The problem people have with this ending is because they mistakenly place the emphasis on the first part of "You're such a loser, Dad/Just enjoy The Show."

The emphasis is actually on the second half, which has been Beane's personal storyline for the entire movie. In the minor leagues--Beane was a minor leaguer for most of his playing career--players refer to the major leagues as The Show. (I'd bet that somewhere on the cutting room floor for this movie there's a line of dialogue that explains this to people who don't follow the game or who haven't seen Bull Durham.) We've seen in the movie that Beane can't enjoy baseball games--as a player or a team's General Manager--because he's so caught up in winning and losing. Particularly the losing part. As he explains to one of the players in a bit of thrown-off dialogue, he hates losing more than he wants to win.

So, Beane loves baseball, but he listens to the games on the radio or keeps track of the score from his Blackberry rather than watching the games in person (or even on TV) because he can't bear watching his A's lose. The daughter's main role in the plot has been trying to convince her dad that he doesn't have to be afraid of his team losing--he could just watch the games and enjoy the incredible stuff they're doing, like a regular person.

She changes the lyrics to the song to teasingly give him that message--"You're such a loser" not in the sense that he loses ballgames but that he's kind of a misfit who refuses to enjoy himself. But when Beane listens to the song at the end, he realizes that he's leaving the team and the daughter that he loves because he's afraid of losing. And that's why he turns his truck around and backs out of his deal with the Red Sox.

It's simple. He accomplished all but if he isn't happy then he isn't enjoying the show. It's what she says with the song no matter what problems you encounter in this life, just enjoy the show.

have you even seen the movie.... Billy is a loser, always was and will be, but he wouldnt have it any other way... partly coz he is a perfectionist amd also his only goal in life is to win....:) and also the love of his doughter, but there he just has to maintain that relations. I know nothing about sports but i do know that if you are the best at the end of the season, people will think you are going to keep it up next season (this is how tickets are sold, sad actualy that is why i dont folow sports)

it does not matter if Casey's lirics say looser or that it was only in billys head... point is that you can never win when you are a perfectionist, there is just no beating youre self, you are always better than you were....

keep in mind just enyoj the show people... :) peace from Bosnia

I think the reason she says "you're such a loser dad" is because the whole movie is about Bill rebuilding his baseball team back up with a cheap budget for the next year, and there are only about 3 to 5 scenes where he is actually spending quality time with his family. She started out saying that he was a great father to make him feel good, even though he doesn't deserve to. Then she starts saying he is such a loser because his whole life is just about baseball and even when he does win, he doesn't enjoy the show. That's why she is calling him a loser.

I am also baffled by this ending and wish it wasn't so.

I'm thinking maybe he is a loser for passing up the opportunity the Red Sox gave him because he is too afraid - connecting to the scene before this where Peter Brand showed a video clip that the baseball player never expected it and just ran first base and didn't know to hit a home run - loser because he had such little faith that he can do it or already did it but still need assurance by winning the last game of the season.

Or se was teasing him since he always thinks he will jinx the game - you're such a loser just enjoy the show you're not going to jinx it.