Just 24 goals have been scored against the Latics, a total lower than both Arsenal and Aston Villa, and the fifth best in the division.
Melchiot told the Wigan Observer: "We defend well together and we did very well again on Saturday.
"If you understand eacsh other and you get into a good rhythm, you know what each other are good at and not good at, and it helps you go that extra mile.
"If one of you gets beaten, someone else is willing to help out - and that makes a hell of a difference.
"The first thing you have to do is make sure you don't lose the game, to help your confidence levels and keep the rhythm going."
Melchiot spent five years with this weekend's opponents, Chelsea, and made 130 appearances at Stamford Bridge.
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