Roberto Di Matteo completes his fifth signing of the summer, having already concluded deals to bring Eden Hazard, Oscar, Marko Marin and Thorgan Hazard to Stamford Bridge, and the Spaniard looks set to solve the club's right-back problem, after Jose Bosingwa left at the end of last season.
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"A new challenge awaits him in the ranks of the Champions of Europe 2012."
As exclusively revealed by Goal.com last week, the move has been on the cards for some time and with only Branislav Ivanovic in the current Chelsea squad capable of playing out on the right, ahead of a long and arduous campaign, the Italian boss has sought to add some much-needed depth to the squad.
Di Matteo told the club's official website: "He is a young player from Marseille, who has come through all the ranks with the youth level of the Spanish team, and he will give us cover at the right-back position with Paulo Ferreira and Branislav Ivanovic.
"It gives us more options for the future and competition. We will see who is going to be playing."
Azpilicueta arrives after a successful two-year stay in Ligue 1 with Marseille, during which he established himself as a regular but following a disappointing 10th-placed finish last season.
The defender follows former boss Didier Deschamps out of the exit door at the Stade Velodrome this summer, after he left to replace Laurent Blanc as the coach of the France national team.
The 22-year-old boasts a wealth of experience, considering his age, having played for four years prior to his move to France in La Liga with Spanish outfit Osasuna, going on to make over 100 appearances for the club in the process and new domestic team-mate Juan Mata welcomed Azpilicueta's arrival after having previous experience with him at international level.
"I used to play with him before the Olympics as well as at the Under 21s and earlier," Mata added.
"He is a strong running right-back who has pace as well, so I think he is already a complete player.
"I played against him when he used to play for Osasuna, and he was one of their best players, which is how he is now here with Chelsea.
"He is such a nice guy, a young player who is very clever on and off the pitch, so he will be very good here."