Ferguson still has sleepless nights over Bayern Munich defeat
Ferguson has guided the Red Devils to two Champions League successes in his 24 years at the club, but reckons they should have won at least twice that.
United were knocked out by Bayern as Arjen Robben's late volley at Old Trafford sent the German giants through on away goals.
"We've only won it three times, which is not enough for this club, and we've been unlucky a lot of times. Other times we've just ballsed it up," Ferguson told The People.
"The reality is we could have won it another two or three years.
Last year still plays on my mind, that Bayern Munich game. Christ, I'm still not sleeping after that! I keep thinking about that game and keep getting angry about the way we lost it.
"We were in complete control until Rafael was sent off and then they came back into it. That result hurt and still does, but against Borussia Dortmund at Old Trafford in 1997 we had about 15 chances and about eight one-on-ones with their keeper.
"If we'd got past Bayern Munich I think we would have reached the final last year and I'd have fancied us against Inter Milan."
United begin their assault on this season's Champions League against Rangers on Tuesday and Ferguson is refusing to take the Scottish champions lightly.
"You've got to respect Rangers and with their history you can't take them for granted," he said.
"I know Walter Smith well and just how organised and difficult to beat his side will be.
"Walter will get a good glass of wine after the match but, hopefully, that's all he'll get."