There's an option to turn on offensive/defensive coordinator speech and subtitles. If you turn on coordinator speech, then the announcers will only speak in a handful of situations (the beginning of the game is the only one that comes to mind).
EDIT: These instructions are from the Xbox 360 version:
From the main menu, go to the "My Madden" -> "My Settings" -> "Game Options" -> "Coordinator Audio" (#10). It can be turned on, turned on for the headset only, or turned off. It replaces most commentary with a tutorial-ish description of what to do on the play. They're certainly less annoying than the announcers. The announcers will chime in at the beginning of the game and a handful of other times for which I haven't identified a pattern yet.
I don't know any other way to get them to talk less other than muting the announcer channel: Main menu -> "My Madden" -> "My Settings" -> "Volume Control" -> "In-Game Commentary". But you explicitly didn't want to do that; I'm only including it for completeness.