The problem we have is not that we can't defend, it's that we can't defend at home. In our away games this season we have conceded 13 goals (average 1 per game). Only Spurs have conceded fewer. At home we have conceded 29 (just short of 2 per game), which is more than anyone else. The same players are involved in these games, so why the difference? To me it is all about the way we set up. Away from home we defend deeper and we hit teams on the break. We are content to play the ball around more without looking to necessarily create opportunities. We also don't seem to mind hitting the ball long on occasion to relieve pressure. At home we are looking to attack all of the time. Our full backs push on a lot more and leave spaces that leave us vulnerable to the counter-attack. If Martinez can rein in our attacking philosophy at home - which may not please some of the fans as it will lead to possession for the sake of it - then I think we can improve our home record markedly.
I can't remember ever seeing such a disparity between home and away defensive numbers before, if anything you'd expect the home ones to be better than the away. The one thing they do seem to show, though, is that away from home we are a very good defensive unit.