The Red Devils missed out on clinching the prestigious accolade after losing 2-0 to Barcelona in Wednesday's final in Rome.
United were close to taking the lead early in the game through Cristiano Ronaldo's shots but Eto'o scored against the run of play to put Barca ahead after ten minutes.
Argentinean sensation Lionel Messi wrapped up the win in the second half.
"We started the game well, and we could have been in front," Ferguson told ITV Sport.
"The (Eto'o) goal was a killer for us. It's hard getting the ball back off them, because they use it so well. They were the better team on the night."
United's backline has been solid this season, with Rio Ferdinand and Nemanja Vidic forming a formidable partnership in the heart of a four-man defense.
But they looked helpless against Barcelona's attacking trio - Eto'o, Messi and Thierry Henry.
"Our defense has excelled this season, they've been fantastic. But they were two very shoddy goals tonight," Ferguson added.
"I don't think we played as well as we can, but we were playing against a very good side, and we've got to give them credit."