United surrendered top spot to arch rivals Manchester City, who had thumped Aston Villa 5-0 earlier in the day, as Anthony Pilkington headed home the only goal of the game in the 60th minute.
Ferguson admits his side were not at the races as they failed to turn their dominance into goals, while the Reds boss also had special praise for Canaries goalkeeper John Ruddy.
"Norwich deserved their win because they worked so hard for it, although we had a lot of possession and one or two half chances. We didn't create enough great chances. It just wasn't our night," Ferguson said on ESPN.
"Their goal was a marvellous cross and a great touch for the header. There was nothing our keeper could do about that. So you have to give credit to Norwich because they battled well, and their goalkeeper had a good night as well, so it is disappointing."
United were without Rooney, who was suffering from tonsillitis, but Robin van Persie and Javier Hernandez both played and Ferguson refused to make excuses.
"You always miss your good players, but we had plenty of good players on the pitch tonight," he added.