After much soul searching, Cotterill has turned down the offer of an Assistant Manager’s role.
Cotterill told bcfc.com that it was a ‘very difficult decision’ to make.
Cotterill and Paul Groves were brought in by Redknapp as his First Team Coaches/Assistants when he was appointed to replace Gianfranco Zola.
The trio helped guide Blues to Sky Bet Championship safety by breathing new life into the team.
Redknapp opted to make his interim deal permanent, but Cotterill remains keen to strike out as a manager in his own right again.
“It was a very difficult decision,” he said. “I have given it a lot of thought.
“But I have decided to turn down the Club’s offer of being Assistant Manager.
“The Club made me a good offer and my decision was solely based on being a number two, whereas really I have been a manager for a long time in my own right.
“Harry Redknapp asked me to come in and help for three weeks and I believe that’s what I firmly did.”
Cotterill, who has two decades experience as a manager and guided Bristol City to the League One title in 2015, says he thoroughly enjoyed his brief stint at the Club.
He was an influence behind the scenes at Wast Hills and the players quickly warmed to his methods and manner.
“I will miss lots of people at Birmingham City I got on extremely well with.
“I’d like to thank the kitmen, analysts, physios, sports scientists, office staff and the players.
“And with the players, the relationship I developed with them on and off the pitch was fantastic.
“They were very receptive in the meeting room, they worked extremely hard on the training ground and the results were there to see – they did really well to get the two out of three wins needed to stay in the Championship.
“Last, but by no means least, I’d like to thank the fans. In the three games they were unbelievable. The support they gave to the players was different class.”
Cotterill has an open invite to attend any Blues match he so wishes.
“If I am not working at the start of next season I have been invited to come to any Birmingham game to watch, which is a very nice gesture.”
Cotterill concluded: “I’d like to wish a great football club all the very best for the future.”