Bad Defensive Habits, Prime Example (VIDEO)

This video shows a goal by Aston Villa last weekend against Chelsea. It demonstrates perfectly, in a single play, two very bad habits that lead to poor defending - first, Mierles doesn't put pressure on the ball, and allows straight ahead dribble penetration - and second, David Luiz watches the ball (the dribbler) and doesn't track the striker behind him, so he gets dragged out of position.