I remain calm.
First, a defeat to Chelsea has no material effect on the final outcome of our CL qualification, which is now in the bag.
Second, we have depth to cope with this injury crisis. Let's assume the following XI, with the estimated amount of their transfer fees in parens.
De Gea (20)
Valencia (17) Smalling (17) McNair (N/A) Shaw (30)
Fellaini (28) Herrera (30)
Mata (37) Di Maria (60) Young (18)
Rooney (30)
Roughly 230m in transfer fee "valued" footballers, which can't be that much less than what Chelsea will put out on the pitch. True, a side may only be as good as its weakest link, which in this case is McNair (can't see Blackett starting), but the point is that we still have some seriously quality out there, players who happen to be in good form right now.
But the important point is to look at the inclusion of Di Maria, McNair and Shaw (seems likely to me, all of them) as an opportunity for them to silence their critics, especially Di Maria.
Win, lose or draw -- so long as the loss isn't "bad" -- I will remain calm, almost serene. We've done the hard work of beating Tottenham, Liverpool and City and have several very winnable fixtures left and there is zero chance now we will be knocked out of CL qualification. And there really was always zero chance of us actually lifting the English prem trophy anyway.