Here are six reasons why FC Barcelona’s defense is dominating this season so far: -> Marc-Andre ter Stegen has given up just two goals — both of which were unstoppable -> Samuel Umtiti has blossomed into a defensive stalwart -> Gerard Pique is once again proving to be the keystone of the team’s back line -> Jordi Alba always makes it back to cut off opposing runs -> Nelson Semedo has added lethal speed to the team’s defensive unit -> Aleix Vidal is playing as well as ever