The Spaniard admits he's still adjusting, however, to Chelsea's style of play.
"I think that full-back is a position where you need to be perfect in defence at first," he told chelseafc.com, "and then you must help the strikers and the wingers to give another option to the team.
"It is true that the easiest is to go forward because everyone prefers to go forward and it is more beautiful to attack than defend, but the most important is to give balance - to know when you can go and when you cannot go.
"It is difficult sometimes," he acknowledges. "I made some mistakes when I started playing this position because it is difficult to know when and when not to, and with experience you start to learn when you must go. Also with the help of coaching staff you see when it is possible."