I think it's an issue that we have no pace thought the middle. Our quickest wide men (relatively speaking), have no targets if they break with pace, so they pull it back and wait for the rest to catch up. I think the idea behind Hugo coming on is to solve that problem, but his first touch has been quite poor so that hasn't really come off this season. When Berba's on, and if he stays forward, he helps a bit because his touch is so good that the ball can be driven to him at pace, allowing more of a time advantage over the defenders.
I'd really like to see Kaca left, frei middle, duff right with Berba up front for a game. I feel if we can get some pace moving around berbatov, we might see some good things happen.