Azpilicueta has been truly magnificent. He does well going forward (despite him being right footed playing on the left) and he's just so damn aggressive defending. He wins the ball in the middle of the pitch often and on the left back he's all the way up the wingers ass, not giving them any space.
I believe he's mentioned that Mou explained and coaches him to to rely on his dominate foot being closer to the keeper. It makes it easier to defend against wide players who like to cut in. He's playing this year for his defensive contributions more than anything, but has shown he is capable of running for 90 mins and putting in the occasional cross with his right or left.