'Error 174' in Yahoo Fantasy

Yahoo Fantasy leagues configured for "Daily-Today" roster changes won't allow you to drop players in active roster positions after the start of a game they're scheduled to play.

If you try to drop a player in an active roster spot after their game begins, you'll see the error message: "A player has already played and is no longer editable for today. (Error #174)".

The player can't be edited until the next day and you'll need to choose a different player to drop.