The 25-year-old joined from Marseille in Aug. 2012 and has made 95 appearances for Chelsea.
Azpilicueta, who is naturally a right-sided defender, was able to secure a regular role at left back ahead of Ashley Cole last season and has kept his place despite Filipe Luis’ arrival from Atletico Madrid earlier this summer.
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Azpilicueta has completed all three of Chelsea's Premier League games this season as Jose Mourinho's side sits at the top of the table with nine points.
Since arriving at Chelsea, Azpilicueta has also made his debut for Spain’s national side and featured twice at the World Cup earlier this summer.