I think the only reason that Man United aren't being attacked by the press as a team in crisis is because Liverpool is doing so badly.
But United are weak at the back this season.
Before today, United were two points behind Chelsea in the EPL and perfect in their Champions League qualifying matches. They're not playing perfect football but they're getting it done, with the occasional good luck intervening (see vs. Arsenal and Sunderland).
And I wouldn't draw too many conclusions about United's defense from today's match. None of their starting defenders today were first choice players. If O'Shea, Ferdinand, Vidic, and Evra conceded three goals to CSKA at home I'd be genuinely alarmed, but the goal were given up by Neville, Brown, Evans, and Fabio. And Fabio was truly, truly awful today. Evans had to clean up after him all over the place, leaving huge gaps in the back line and CSKA has the quality players to take advantage.
Thankfully, Neville, Brown, Evans, and Fabio won't be starting at Stamford Bridge on Sunday. Evra and Vidic will be back. I think Ferdinand should take as much time as is necessary to get healthy, even if it takes a month or two.
I think the central midfield failed again today. Fletcher had a bad, bad game. Scholes wasn't very good, except for beating his teammate to head in United's second goal.
Gabriel Obertan already looks a lot more dangerous than Nani.