N'Zogbia held talks with Birmingham after the two clubs agreed a fee, but the move broke down over personal terms.
"I feel that whatever the thoughts were and whatever the different options were that he had to consider, that is well in the past,'' said Martinez. "Now he is ready, he is focused and all he wants to do is help Wigan Athletic to carry on being competitive.
"From his position, he is ready to show everyone that he wants to enjoy his football with us.''
Asked if N'Zogbia was in his thoughts for the Sunderland game, Martinez said: "He is, but not just because I'm saying it. It is the way he has been working in the last five (training) sessions. I don't blame Charles, I just blame the situation. I think the authorities in football should really look into it and we should help the players on the human side, to help them focus on concentrating on their jobs.
"Having the transfer window open while competition is going on is not healthy - it doesn't help anyone, not just Wigan Athletic. I think you could go in every single dressing room in the Premier League and in a different manner, everyone has been affected.
"It is important that the players have time to think about their futures and the next step for their families, and there is a period to do that in the transfer window. But it shouldn't be while competition is going on - it is disrespectful to the fans and devalues the league as a whole. We should close the window before the first game starts.
"But I have been delighted with Charles' attitude. He looks focused and concentrated. He made the final decision to stay - it wasn't imposed on him at all, so we have signed a new player.''