That's the verdict of former Stamford Bridge favourite Graeme Le Saux in the wake of the Spain international's fine start to the season.
Azpilicueta has continued to impress for Chelsea on the right-hand side of their three-man defence.
And he's made an impact going forward too, providing a flurry of assists for countryman Alvaro Morata.
Azpilicueta is in the sixth season of his spell in west London having joined Chelsea from Marseille in 2012.
Le Saux, who used to play left-back for Chelsea, doesn't think the 28-year-old gets the credit he deserves though.
Asked to name his old side's unsung hero, Le Saux told Starsport: "It would have to be Azpilicueta, he’s assisted Morata on four goals, is versatile and has been their unsung hero for a few years now.
"He hardly misses a game and offers real quality in possession; I can understand why he’s easy to overlook but would never underestimate his importance to the team."
Azpilicueta played right wing-back during Chelsea's 1-0 defeat to Manchester City before the international break.
He'll be hoping to help them get back to winning ways against cross-city rivals Crystal Palace on Saturday.
Chelsea can move as high as third in the table providing they win and results elsewhere go their way.
Palace, meanwhile, are yet to score or pick up a point in the Premier League this term.
Graeme Le Saux spoke to Starsport on behalf of Betfair. For more from Le Saux go tohttps://betting.betfair.com/football/graeme-le-saux
