At home we are set up in a more attacking formation with the back four playing a higher line. That makes us vulnerable, both to passes dissecting the two CBs or over the top. This is particularly likely when the pairing is Tarks and Keane. The lower block away from home avoids most of this. It's also clear that Moyes had the team working all week on a more aggressive central midfield that could block off the supply of passes through those channels, forcing play onto the flanks and crosses that are easier to deal with. A more mobile CB pairing and/or a more defensive-minded 6 are obvious if not necessarily short-term solutions. Until then, expect to see the problem at home persist, particularly on the counter-attack.