With a host of new faces arriving in the summer, the team struggled in the opening couple of weeks of the Barclays Premier League season, shipping 10 goals in their opening two games.
But performances have improved since as Latics have now kept two clean sheets in a row while on their travels - something which delights Martinez.
"We've got a few new players playing in defence," explained the Spaniard to the Wigan Observer.
"You need to have that understanding; you need to react with each other and that takes time and playing minutes. The concentration was right on Saturday. Birmingham have got a very effective approach.
"If you don't get close to the second ball, they're going to hurt you and I felt we restricted Birmingham in that respect a lot and that's full credit to the defenders and their concentration.
"But it's important that the longer we play, the better we get in those departments."