The penny dropped behind bars, as he began to physically and mentally rehabilitate. He focused on exercise and weight training, and earned his stripes playing league and 'crash', a prison version of bullrush.
Once he was released, after more than two years inside, he launched himself into the sport again. Ma'u was good enough to be picked up by the Auckland Vulcans, but was unable to travel to Australia to away games due to his conviction. But his talent was noticed, and he joined the Eels in the middle of 2013, after the club eventually secured him a visa. From there, his rise has been as steep as his previous fall.
After half a season with the Wentworthville Magpies in the NSW Cup, Ma'u claimed a starting spot ahead of the first round of the 2014 season. He destroyed the Warriors in that game - 14 runs for 185m - setting a standard that has endured since.
"He is quietly spoken and humble, but he can be a bit intimidating if he is not saying anything," laughs Kiwis teammate Jason Taumalolo. "[But] he is one of those old school players that does everything 100 per cent and doesn't worry about putting his body on the line."
Ma'u is grateful for his second chance - and never forgets his troubled past.
"I was always going to keep on trying, until someone told me that it was too late," said Ma'u. "I kept grinding away and I was lucky enough to get a crack with Parramatta. It has helped me heaps, when I look back and see where I have come from. I know where I have been ... [that] has helped me play hard."
Ma'u will be a key in a Kiwis pack tonight that has a huge responsibility. With a raw backline outside them - exacerbated by the late withdrawal of Shaun Kenny-Dowall yesterday - New Zealand hopes hinge on forward dominance, on blowing the Australians away through the middle, as happened in Brisbane last year.
"He's a tough player and doesn't worry about taking those tough carries when no one else wants to," said Taumalolo. "We need players like that, [who] will set the platform [and] don't care who is standing in front of him."