This.
Manchester United's problem isn't the lack of big man up top. It's the lack of a creative force in midfield.
Valencia, Nani, Young are all certainly capable of supplying the forwards with good crosses or pull backs.
United look less effective up top in recent times due to the effort Rooney and Berba have to put in coming deep to get the ball of the midfield.
Manchester United are fine as they are in terms of Goalkeeping, Defence and forwards. They lack imagination and spark in midfield and lack a midfielder in the mould of say Lucas at Liverpool.
Thats not particularly accurate, Rooney hasn't ever HAD to come deep yet he's always done it, which has frequently over the seasons cause essentially a lack of upfront presence, while you could say him dropping deep might help more now. It really doesn't, if he's playing as a striker, play as a striker. If he was running in behind as he did, then a lack of a creative central mid would be less of a problem. When Rooney drops deep crossing into the box is less effective AND because the one isolated striker is much more easily marked it takes a much better ball through the defence to set someone up.... Rooney isn't generally capable of that.
If he was upfront, and two strikers were giving the defence a hell of a run around AND available for crosses. Then their quality wingers could provide two hard to mark strikers with good service........ that doesn't even require the central midfielders, it helps, no end. Especially if you have a Lampard type to run into the box as well. With Rooney pushing the back four deep trying to get to crosses, that leaves space for the midfielders, even less good midfielders, to run in to the edge of the box.
Basically Rooney needs to stop dropping so deep, there is no need, its hurting the team, the less good the midfield gets the MORE important it is for Rooney to make it harder for the defence, not easier.
If Rooney was actually fantastic in midfield, I'd drop him back fully and play someone else up top, he's not, his defensive work is, meh. He fouls more than he tackles, his passing isn't very good and he doesn't go on those powerful driving runs he used to either. Play a good striker as a good striker, not an average midfielder.