There is no way to make up for an injured superstar on a fantasy football roster, but you can find replacements who can lessen the blow going forward.
Arian Foster was the latest big name to suffer a season-ending injury after reportedly tearing his Achilles Sunday. If you had him and Jamaal Charles on your roster, things are not going your way. Of course, these are real people suffering real injuries, so maybe consider that before crying about how it affects your team—especially because in your situation, you can do something about it.