Man United fans; Are we in danger now we've lost Rio n' Vidic?

Whenever we're on top form, and all players are fit, we're great everywhere all over the pitch, attacking, midfield, and in defence. But now Rio n' Vdic are out for a few games, does that change things? are Chelsea gonna' sneak up behind and over-take? and who are we gonna use now as our centre-backs? Brown n' O'Shea? is Neville gonna' be at right-back?