Midfield for me, allied to our tactics.
If you have a quality, balanced, midfield. you can dictate how the game pans out. Play keep ball to take the sting out of it, constantly offer the threat of the breakaway, win the ball back in the right areas. We really struggle to do that because we don't have any well rounded midfielders. Gana's great at breaking play up, but he can't pass (same for McCarthy), Rooney can pass but hasn't got the legs to press and get up and down, Schneiderlin has just been an abomination. Davies is the closest we have to a proper box to box midfielder but he's far from the finished article.
It means we can set up in a style which is supposed to be a threat on the counter, like we did against Arsenal, but we can never utilise the counter because we can't pass the ball to the right players. Alternatively we can try to be combative and force the home side back through hard work, like we did against Bournemouth, but then we lack the creativity to actually do anything about it. When we move to add more creativity, as we did by bringing on Rooney and Bolasie in that game, we lose the solidity and suddenly they're going right through us.
It's been a problem for a few years. Bring in a midfielder or 2 who can stick their foot but are equally comfortable passing the ball forwards and suddenly we'll look a totally different proposition. I've said before, we've got some good players but the areas we're lacking in undermine us massively.
