Mandaric is in the process of putting together a shortlist of candidates to succeed Dave Jones, who was axed on Sunday.
He told talkSPORT said: "We need somebody to lift the team and give us a better chance to win enough points to stay up.
"We are putting together a shortlist of maybe four or five candidates that are available that we believe can do the job and on Wednesday and Thursday, we will start to interview these people.
"Hopefully, we will make a decision as soon as we can, but the most important thing is to make the right decision.
"We need to have a big, strong character. It is not going to be easy. There are a lot of good managers so it is going to be a challenge to bring in the proper guy.
"It will not be fair to tell our supporters that we will have the new manager by the weekend. We need to have the proper man. That is more important than bringing him in before this weekend."