Sir Alex: United to learn from Barca mistakes
United produced a lacklustre display to lose 2-0 to the Spanish champions and Ferguson said lessons would be learned.
"You can look at reasons and excuses and it's always better to look at the reasons," Ferguson told reporters.
"They are quite clear what they are. If there were no reasons at all then we would be worried but I think there were valid reasons so we will move on.
"I don't want to go into what those reasons were but I took the DVD on holiday and watched it and went through everything and it made me feel more honest about the whole build-up, everything.
"Did we have the right hotel?, things like this, the training, everything. So I am quite clear about where we are.
"I think those problems can be put right and they certainly will be put right."
United could have had an easier away trip than the long flight to Istanbul where they will take on Besiktas.
"There is something to admire about the fanaticism," said Ferguson of games in Turkey. "The stadium is full at 12 o'clock on the day. It's amazing how they can generate that fanaticism but you have to deal with it."
Ferguson must select a line-up that can help United start with a victory while casting one eye towards Sunday's Manchester derby when they face City at Old Trafford.
Ferguson's team selection for Saturday's impressive victory at Tottenham offered clues to his European line-up with veterans Ryan Giggs and Paul Scholes involved at White Hart Lane and unlikely to figure in Turkey.
Besiktas lost the first Turkish Super League derby game of the season against arch-rivals Galatasaray 3-0 on Saturday but Besiktas coach Mustafa Denizli said the defeat would not affect the team's performance against Manchester.
Denizli was criticised for a surprise line-up with Brazilian Bobo, who led the team to the Turkish Cup this year, left on the substitutes' bench.
"From now on we are focusing on Manchester United, and I'll see how much our work pays off on the playing field," said Denizli.