The Toffees boasted the third-best defensive record in the Premier League last season, but they have already shipped 13 goals in the current campaign - more than any other team.
However, Martinez is confident that his players have the quality to rectify the problem going into Saturday's Merseyside derby against Liverpool at Anfield.
"That's been an area that we've been quite poor and it's something we need to improve. Sometimes you get situations where when you are so good as a team at something that you could take it for granted and then you get a little bit of misfortune in one or two actions early in the season and the ball ends up in the back of the net, and all of a sudden it seems the confidence is not the same and you don't defend with the same intensity," he told reporters.
"You look at the experience we have in the team, we haven't made any major changes in those positions. Now what we want to do is make sure we have more focus, better concentration, better communication and just face that challenge of getting back the standards that we have as a team defensively.
"It's not something that we're aiming for, it's something that we have, and it's a big difference. But clearly conceding the amount of goals we've conceded is not something we want to accept. We'll always approach games to win games but it's important we don't become a team that concedes games cheaply."
Everton are currently 14th in the Premier League table having picked up just one win from their opening five outings.