If the term Mail it in
originated from the movie, Van Wilder. It has evolved to be used more so in sports now. When a team actually has a chance or shot to win or contend, and they don't even put forth their best effort. Or perhaps settling for par in a quarter to save someone for later in the game or in 1 game in a series of games, or in a playoff stretch. When a team or manager doesn't believe they have a chance, but the fans or players actually do, and a critical decision is made that pretty much lets everybody know.
Fan,"They are only 4 games out with 2 weeks left, and Griffey isn't even the lineup, I can't believe they mailed it in".(the season) Fan,"bottom of the 9th, up 1 run, and you don't bring in the stud closer because you used him last night,they are mailing it in". "The manager is goin to mail it in".