The Englishman's talent had given him opportunities at Chelsea, Tottenham Hotspur, Arsenal and West Ham United, but his temperament had caused the door to close every time. A tip off to Neil Lennon at the end of last year ended with the 21-year-old defender arriving at Celtic Park. Now Blackman believes that, after a chaotic start to his career, he has found a place to settle and finally prove that those who dismissed him as more trouble than he was worth seriously undervalued him.
As he took some time off from the heavy pre-season schedule here in Bad Gogging, 90 minutes from Munich, a relaxed Blackman explained: "I've felt more at home here than I have anywhere else. I moved from club to club when I was younger. I wasn't settled, I didn't have my head right. I played for Arsenal, Tottenham, Chelsea and West Ham with guys like Jeremie Aliadiere, Justin Hoyte, Kanu, Robin van Persie and Freddie Ljungberg. We'd join in with the first team for a while, just to get a taste of it.
"I had a bad stigma that followed me around, though. I just wanted someone to take a chance so I could show I wasn't who they thought I was."
Blackman acknowledges his bad-boy reputation was a major obstacle in establishing himself at any club, at any level. For a youngster who had started at the top, the rapid descent was hard to accept, not least because he did not believe he was the man most people perceived him to be.
"People think I'm a guy with a temper, a short fuse," he said. "Once you've got that label, it's hard to shift it. The slightest thing could happen in training and people would say, 'There he goes again'. Some people judged me in a different way. I'm passionate about football. It's not a temper. At times someone could tell you something as a senior pro. If you're younger, you're not supposed to answer them back. I had my views and wanted to express them. Maybe I didn't put my points across in an orderly fashion. Everyone has their opinions. You can't change that, if that's how they see you."
Only after Lennon was alerted to his predicament and potential did Blackman's career curve revert to a positive direction. However, immediately prior to that call, he was as low as any professional could go.
"I was out the game for a year-and-a-half before that," he explained. "I spent my time at a soccer school, the Jamie Lawrence Football Academy, which you pay a fee for on a daily basis. You work like you're at a club, but, at one stage, I couldn't even pay because I didn't have any money. I got in touch with an agent and he said he would pay it for me. It was a big reality check for me. In fairness, it was what I needed to open my eyes. There were times it was really hard, but I had to show a bit of mental strength to get through it."
From adversity – and poverty – a new player has emerged. "I'm happier now because the whole thing has made me wiser," reflected Blackman. "I was playing football with my friends at a local five-a-sides in London. That was it. There were no offers the whole time. Whenever someone heard the name Andre Blackman they said, 'Nah, I don't fancy him'.
"I never thought about quitting. I always thought I'd be able to make it. Then a friend of the manager recommended me and asked if I could come up for a trial. I definitely appreciate this chance after everything I've been through. I was kicked out of football early on in my career. I wasn't nervous, I was just anxious about the trial because of everything that had happened."
Lennon recognises that, in Blackman, he has a young player who has already overcome much more than would be required to break anyone whose resolve was not cast in iron.
"I'm thankful Celtic have given me the chance to express myself," said Blackman, who started against Ausgburg in the opening game of the tour on Tuesday. "I know I have to grab it with both hands. This is an important season for me. Everyone wants to play; it's down to the manager.
"There's a good set of backroom staff and a good manager willing to help me. If I'm going wrong, they can pull me aside and tell me what needs fixed. I've never had that at other clubs. I needed somewhere to go to show I had changed and the views people had of me were wrong."