The Blues are currently leading the way at the top of the table, one point ahead of Liverpool.
During their campaign under manager Jose Mourinho, Chelsea have kept 14 clean sheets with seven games left to play.
"We are defending well because everyone is defending," Azpilicueta told Chelsea TV. "We are not conceding goals because everyone is doing their jobs.
"We are keeping a lot of clean sheets and why we are doing well is because of the team. We have very good centre-backs, quality players. John [Terry], Gary [Cahill] and David [Luiz] are very good centre-backs and the relationship between them is key for the team."
The Blues will take on Crystal Palace at Selhurst Park on Saturday.