Phil Simpson heard he had been replaced at Tooting & Mitcham from an ex-player.
On Thursday, Tooting announced their former midfielder Craig Tanner was taking over the management reins at Imperial Fields from Simpson, who ended last season as caretaker manager.
Simpson was still waiting for an answer on his future and whether he will stay on as manager when he received a call from one of his former players asking if he had heard the news about Tanner.
"I am very disappointed," he said.
"Not by the fact that I didn't get the job, if they feel I am not the one then that's fine. But I am disappointed about the way they have gone about the whole thing.
"I know caretaker manager means temporary but they could have rung and told me - but nobody said anything to me.
"Instead, I found out this way, one of the ex-players phoned me and told me to have a look at the website.
"I heard rumours about this guys name back in March but I just thought OK and got on with the job I had to do.
"I say good luck to him, he is going to be working in what I feel are not very professional circumstances.
"I have been very grateful for the opportunity but the way they have gone about the situation they could have handled it much better.
"I wouldn't be surprised if they have sorted other things out behind my back as well.
"They could have appointed him any time."
While waiting to find out if Tooting did want to keep him on, Simpson has gone back into corporate banking and is now unsure what is next for his footballing career.
"I resigned from a job to take on the manager's job at Tooting so I really put myself out for them and they should have handled it much better," he said.
"But now I have gone back into corporate banking - at least I know I have a decent wage and it is something I enjoy to do.
"It works out better for me financially but in a football sense they have let me down.
"All I can say is good luck to him and I wish him all the best."
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