An emergency procedure to remove his appendix resulted in Chapman being offered the painkiller OxyContin. Two days was all it took to get hooked.
Chapman had struggled with social anxiety, depression and other mental health issues since he was a teenager, but that was all blown away by this wonderful new drug in less than 48 hours.
"I felt smarter, funnier and felt like I was walking about an inch-and-a-half off the ground," Chapman says in the first episode of his new podcast, Charges with Rex Chapman.
He was never a drinker, but Chapman always had an addictive personality. Gambling — particularly on horse racing — had been a major vice since his college days and now he had another to add to the list.
'I was perfectly messed up all the time'
Chapman became a full-blown drug addict, all the while raising three kids with now ex-wife Bridget. For 18 months his personal and family life deteriorated as drugs became his best friends. The former NBA star was going through 10 OxyContins and 40 Vicodins a day.
"I was just chewing them up, no water or anything," Chapman says. "Good thing I didn't drink, because I'd for sure be dead.
"I would just chew them up to get them into my system earlier. I was perfectly messed up all the time."
It wasn't until Chapman's former coach at the Suns, Danny Ainge, confronted him at his modest apartment that he made an important move. Told he looked terrible and was letting down his wife and kids, Chapman entered rehab.
It was there he was informed getting off a painkiller as potent as OxyContin would be just like seven days going cold turkey for a heroin addict — a revelation that terrified Chapman.
"They were right. It was awful," he says.
"It's synthetic heroin, it's synthetic morphine. It's too good," Chapman adds of OxyContin, saying it should only be available to terminally-ill patients or people with major injuries like compound fractures.
Six months after leaving rehab for the first time, wrist surgery meant Chapman was prescribed Vicodin. He didn't tell the doctors about his drug addiction, and believed he would be able to handle the more mild painkiller because it wasn't as strong as OxyContin.
But in retrospect he describes himself as a "coward" for not being upfront about the extent of his issues.
For 10 years between 2004-2014, Chapman was addicted to Suboxone — a drug designed to help wean addicts off opioids.
"My life just kept getting worse and worse. My decisions kept getting worse and worse, until I'm gambling everyday, I've gotta have my medicine everyday," Chapman says on his podcast.
The day that changed everything
Then came the high-profile run-in with the law that showed how far Chapman — who estimates he made around $54 million during his basketball career — had fallen.
Going broke, Chapman was at an Apple store in Arizona in 2014 when he started stuffing $18,000 worth of products into his bag with the intention to pawn them later to pay off gambling debts.
It was an ill-conceived plan for any amateur thief. For a man well known around those parts and an easily recognisable 193cm-tall 12-year NBA veteran, it was the definition of stupidity.
"I'm running low on money, I'm running low on drugs and I'm in an Apple store out of my mind and there are people all around and I just start putting stuff in my bag and left," Chapman says.
"I don't know — I should know — that I'm Rex Chapman the basketball player, who everybody knows here. Everybody.
"I can't see it, I can't see any of it. I can't see that what I'm doing is illegal and wrong and criminal. I can't see that anybody knows me."
Arrested later by six cops as he prepared to leave home to pick up his two daughters from school, Chapman was thrown in jail where he shared a cell with the naked man masturbating. He remembers wearing a shirt with "basketball never stops" written on it the day he caught a glimpse into what his future looked like if he didn't make some serious changes.
'I always felt like a fraud'
Admitting he felt "broken" after being released from prison, Chapman went back to rehab, this time in his home state of Kentucky. He started on a journey of self-reflection that created the foundation for him to climb out of the abyss.
"I always felt like a little bit of a fraud, just from a young age," Chapman says. "People, they had a view of me or I thought they had a view of me as this All-American white kid and I had apparently sold out my whole f***ing life to that ideal, knowing that's not who I was inside.
"I'm a flawed dude, I've got no patience, I have all kinds of warts, I'm depressed — but it was the first time in my life I thought, 'Alright, now the facade is gone, now I can just be me, but I gotta get better'."
Having checked into rehab at nearly 120kg, Chapman kicked his drug habit, lost weight and moved out to Los Angeles, spending time living on various friends' couches.
The offer of a low-profile sports media gig enticed him back to Kentucky and from there Chapman has turned everything around.
He's now a social media phenomenon with more than 1.1 million Twitter followers, who enjoy his slew of viral video clips. Such is his Twitter fame, many who weren't around during Chapman's playing days might not have any idea he played in the NBA for a dozen years.
His mugshot and reports of his arrest still come up when you Google his name, but Chapman is determined to let people know it's possible to bounce back.
