United, who have reached the Champions League final three times in the past four seasons, failed to advance past the group stage this season after dropping vital points drawing and losing to Basel.
They now face Ajax in a round of 32 first leg game - their first at this level of European competition since they played a UEFA Cup tie against Rotor Volgograd of Russia in 1995/96 when they were beaten on away goals in the first round.
Ferguson, talking ahead of their trip to Amsterdam, told FIFA.com that United's early exit from the Champions League was a blip and as much down to bad luck as anything else.
"I feel we had the ability to go all the way to the final," he said. "Luck wasn't on our side, but I think we've got the ambition to compete with Barcelona and Real Madrid, and I don't feel we're that far away from them. I'm sure we'll show that soon."
"We've had our ups and downs and we've been unlucky with injuries," Ferguson added. "We've had a lot of them, which you don't expect, and we've got people like Nemanja Vidic and Darren Fletcher out for the whole season.
"You can replace your best players for a game or two, but you really notice the difference over a longer period, and that's what's happened to us.
"Even so, we're fighting hard to win the premiership again and there's a lot of merit in that. Obviously I'm optimistic about our chances."
"When to retire is difficult. Do you quit too early or go that one too many games and let people see you on the slide? Retirement is just a decision that I have to take my time with because I feel different after each game," Giggs told the Daily Telegraph.
