The former Arsenal, Tottenham and Portsmouth youth was given a second chance by Hoops boss Neil Lennon in January and after a period of uncertainty, the 21-year old now knows what he has to do to make it at the top.
Blackman could not hold down a club during his younger days mainly because of a bad attitude which temporarily ended his fledgling career in 2010 when he was discarded by AFC Wimbledon following a stint with Bristol City which followed trials with Celtic and West Ham United.
Now, however, Blackman is looking to repay the faith of Lennon who rescued him from playing five-a-side matches with his mates.
"A friend of the manager recommended me and asked if I could come up for a trial," he said.
"I was out the game for a year-and-a-half before that. I spent my time at the Jamie Lawrence Soccer School, which you pay a fee for on a daily basis.
"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. 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.
"I'm happier now because the whole thing has made me wiser.
"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. There weren't many opportunities to go and try and play professionally."
He added: "I never thought about quitting. I always thought I would make it. 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.
"I'm just thankful Celtic have given me the chance to express myself. I know I have to grab it with both hands."