In an interview with Champions magazine, Fergie said, "The trouble with 4-5-1 is that it doesn't give you enough points of attack and if Rooney and Ronaldo come deep to defend or cover, your lone striker can get isolated. We used to play 4-4-2, with one player just behind the striker, because it gives you more options, more threats, but 4-3-3 makes the best use of the players we have.
"It keeps Ronaldo and Rooney forward, where they do most damage, and gives us more points on the pitch from which to attack. Manchester United just can't play defensively. The fans would not stand for it. It's just not United. This club has a kamikaze streak, which in a funny way, I rather like.''
Well we’ve had to stand for it for three years now: still better late than never Alex.