The England full-back, handed a 14-month ban for taking cocaine, has signed a four-year deal with Wigan Warriors as he bids to rescue his career in 2019.
Ex-Leeds star Hardaker is free to start training with the Super League club in September ahead of his suspension expiring in November.
But, in an in-depth interview with former Great Britain winger Brian Carney, he has spoken publicly for the first time about the circumstances surrounding his dramatic downfall.
News of Hardaker’s failed drugs test came to light just two days before Castleford and Leeds – who meet tomorrow night at Magic Weekend in Newcastle – faced each other in October’s Grand Final.
Hardaker was immediately suspended and favourites Castleford, despite romping to a first League Leaders’ Shield, were outclassed by Leeds in the title decider, missing the chance to become champions for the first time in their long history.
He recalled what happened when he took the phone call from his agent detailing that UKAD (UK Anti-Doping) had contacted Tigers.
Hardaker, 26, said: “My mum had the phone and she was in tears making all sorts of noises.
“I thought something tragic had happened. I took the phone and just froze really. I’d not told my mum about this so no-one really knew I was trying to keep it hidden.
“I put the phone down, drove off and sat on this grass verge near a canal contemplating life and thinking what had I done.
“I didn’t know what to do with myself. I literally got home, packed a bag, looked for my passport and thought ‘I’m buggering off’.
“I spoke to my girlfriend and we went to the Lake District and got a lodge for five days.
“I had a call from Daryl (Powell) saying I’m banned by UKAD and whether I knew what it was for.
“I told him and he told me obviously I wouldn’t be involved on the Saturday, it was a big blow and he’d speak to me another time.
“But I didn’t speak to anyone for about a week. I hid in Cumbria and only turned my phone on to see the Grand Final score.
“That hit me quite hard. All the boys were super excited. It was the first time Cas had ever got to a Grand Final and I felt I’d let down not just my mates but the town. The town was buzzing all year.”
Hardaker, who won the treble and Man of Steel with Leeds in 2015, continued: “I got home and didn’t leave the house for four weeks.
“Some of the players contacted me but I didn’t know what to do. I felt so embarrassed. I didn’t know whether with the disappointment of the Grand Final if I’d get blamed for it which would be rightly so.
“But then four or five of the boys texted me to say it’s not my fault. Jesse (Sene-Lefao) sent a pic and put Zak on his (wrist) band. They said it wasn’t my fault but I take it quite seriously that it was.
“I feel I’m probably not solely responsible but highly responsible for what happened in that Grand Final.
“I firmly believe if I’d have played we’d have won. I put that on my shoulders 100 per cent.
“I’ve said sorry to all the players, met them all and they say it isn’t my fault. But I’m most disappointed for the fans. It was such a good year. I’ve spoken to a lot of fans and most said it’s not my fault and not to get upset but others put all the blame on me.
“I am really sorry and I told the coaching staff and everyone else.”
Hardaker, who has been working in telesales for one of Castleford’s sponsors, was sacked in February and his reduced ban, due to mitigating factors, was announced at the end of last month.
He says being away from rugby completely has made him realise Wigan’s lifeline is a last chance in the sport that he insists he will take.
Wigan chairman Ian Lenagan said: “This wasn’t a decision that we made lightly.
“We had extensive conversations with Zak and his family before making our offer.
“We encountered a man who, after eight months of reflection, openly admits that he has made a series of significantly poor decisions over the past few years.
“We saw someone who recognises that this is the final opportunity to focus on delivering the achievements his talent should generate.
“My team at Wigan will manage, mentor and test him through this period of rehabilitation and development and, hopefully, guide him back to being one of the best players in Super League.”