Demba Ba's spectacular 49th-minute volley and a stunning Petr Cech save from Javier Hernandez helped Chelsea set up a Wembley semi-final with Manchester City on April 14.
Substitute Robin van Persie spurned two late chances as Chelsea ended United's hopes of a first FA Cup win since 2004 and a first double since the 1999 treble-winning season.
Ferguson, who was without Wayne Rooney due to a groin injury sustained on England duty, said: "Over the 90 minutes only Antonio Valencia reached the standard we expect of them," Ferguson said.
"Phil Jones (did) for a good part of the game, of course, and David de Gea did well, but in terms of the 90-minute performance Antonio Valencia was the only one."
Ferguson also felt Cech's save was the key moment and added: "Cech's save from Chicharito was unbelievable. He made a similar save in the first (game) from one of his own defenders. I think if we had got that goal then we would have been okay.
"It may have gone to extra-time, of course, but it would have brought us back into the game and we didn't need to go chasing it. Robin had a chance from a header, a couple of headers actually. One he really should have scored but he put it over the bar.
"It was disappointing because we are better than that. We didn't play as well as we should have done in the second half."
United's sole focus is now on wrapping up the Premier League title.
They hold a 15-point lead over Manchester City, their next opponents in the competition next Monday.
- Sports & Recreation
- Petr Cech
- Antonio Valencia
- Robin van Persie