Hernandez play off the last man created alot of space for our wingers and Rooney to move into. It constantly put the opposition defense under pressure. Meanwhile Rooney was capable not only of scoring, but also creating and distributing the ball with more space and time. It also took the pressure off our midfield somewhat.
We were a much more fluid attacking unit with Hernandez and not Berbatov. We saw with the FA cup semi final when we brought back Berbatov in, that we struggled to move the ball around with his hold up play and Toure capitalized on that.
Berbatov has been good in the last few weeks, because we've closed the play down against poorer opposition, but as we saw on wednesday, once the pace comes back into the game, he goes missing big time. Thats not to say that Rooney wasn't dross, but Berbatov hardly touched the ball all game.