Azpilicueta, 22, who started his career with Osasuna, has played for his country at various youth levels (including at this year's London Olympics) and is probably being bought as a back-up to Ivanovic (who has scored 5 goals in the last 8 premier league games, by the way!), rather than as straight up 'competition'.
For some reason Chelsea have not revealed the length of the Azpilicueta's contract, but we can expect it to be 5 years, given his age, and the fact Chelsea are buying his potential at this stage more than anything else.
A statement on Chelsea's official website read: "Chelsea is delighted to announce the signing of Cesar Azpilicueta. The 22-year-old right-back, who recently represented Spain at the London Olympics, arrives at Stamford Bridge following a two-year spell in France's Ligue 1 with Marseille."
Azpilicueta joined Marseille in 2010 from Osasuna, and made 69 appearances for the French team. He would have made more except he suffered a serious knee injury in his first season with them. But don't worry too much about his knee, as he came back from that injury and quickly established himself as Marseille's number one right back.
Azpilicueta is now Chelsea's fourth Spanish player, and with the help of Mata, Torres and Romeu, should bed down quickly.
Brian M Logan