As a defender you have to be retarded to stick out a leg in that position, if the ball is going the opposite side and you're kicking out away from goal that is one thing, but without knowing who is around you or being able to see what is going on with other defenders, there is only so many directions you will deflect the ball sticking out a leg towards your own goal, it's just something you don't do in general.
That we are in the situation where we choose between Gibbs or Monreal at left back is a joke. Gibbs hasn't at any time at Arsenal shown a hint of talent defensively, after 2-3 years as a youngster he should have been shoved out the door, instead we give him pay rises and new contracts. He can't god damned defend, at all.