I don't like playing 3 in the back, never have and I doubt I ever will.
I would love to see a 4-3-3 formation though, I think that might even suit us more than the diamond or the 4-4-1-1/4-2-2 (whichever you want to call it).
In my honest opinion this would be our best XI:
Some of you may not agree, but I think this could work out well.
The reason I chose Nani over Valencia is his "fluidity" in attack, or should I say his ability to alter positions with other forwards and make it work, it would make us a bit more unpredictable and harder to mark when going forward.
Ofcourse in no way is Valencia a bad choice, just had to pick one and I believe if everything was clicking Nani would be a better fit in this type of formation than Valencia.
He can always be brought off the bench in this case, and it's not like we'd play this every game, plus don't forget about rotation, so yeah....
You should also notice I "placed" Nani wider out wide than Kagawa is out left. The reason is that while the idea of Kagawa and Rooney both being able to switch their positions might be a great thing to see, neither of those provide any real width. With that being said, it's not as if Nani's as out and out a winger as Valencia, but he's more than capable of providing real width with the added bonus of always being capable of going past a man and/or driving inside.
RvP is obviously also capable of playing behind a striker and out wide (that's not to say he excels in a wide role, but just like Rooney is capable of moving there for the sake of the attack as a whole), and that leaves us with 4 top class players up front all being able to play in eachother's positions, with the added bonus of having someone like Cleverley (or Anderson if you prefer) in midfield that has a lot of drive in his game, and is a good quick 1-2 touch passer that is actualy able to open up some space on his own, and you've got a hell of a team to defend against.