Sorry, but it sounds like you've activated the injury bug.
You can not I repeat
NOT select "Create Plays" at any time during your career from the clipboard. Once you select it, all injuries are frozen for the entire NFL which means all those that are injured will stay injured for your entire career and nobody else in the entire NFL will be injured.
You'll have to start over and again...do
NOT choose "Create Plays or is it Play Creator?" anyway, whichever, do not choose.
You can create new plays either in the main menu before you begin/load your career and then upload/download them from Gamernet or you can edit plays during a game and save them.
This will be addressed (fixed?) in the upcoming patch would should be out in around a month.