The Scottish boss believes the Red Devils possess a "very strong" squad but says the Spanish giants are favourites for victory in this season's Champions League
The Red Devils failed to progress beyond the group stage last time out, but could seal qualification for the knockout stages with a win against Braga on Wednesday.
But Sir Alex has identified the La Liga pair, along with German champions Borussia Dortmund, as the Old Trafford outfit’s main rivals in reaching the final at Wembley in May.
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“You can’t look past Real Madrid and Barcelona, that’s fair to say, and I do think Dortmund will be about the Champions League this year,” Ferguson told reporters.
"If you look at their league form, 11 points behind Bayern Munich, you can tell they’re preparing themselves to do well in the Champions League.
"Those three teams have outstanding chances and I hope we can join them because we have a good squad of players. We’ll need to perform at a really high level to win it."
Despite his confidence, Ferguson is under no illusions about the difficulty of progressing even though his side have amassed a maximum nine points from their opening three encounters.
Braga provided a stern test for the three-time European champions at Old Trafford and Ferguson knows they will be even harder to overcome on their own patch.
He said: “Braga’s record in Europe is good, and particularly at home they carry a threat.
“It’s an important game in terms of if we win we’re through to the next stage. That’s the important part of tomorrow. Hopefully we can manage it.
“I’m hoping we can get to the next stage because it you look at the squad it’s very strong.”