Grant Hackett is adamant he was not under the influence of notorious prescription drug Stilnox when he was booted from a Virgin flight after allegedly giving another passenger a nipple cripple.

What says so much about how far the 35-year-old swimmer has fallen is that not even his closest supporters know whether to believe him.

Hackett says he was only intoxicated when he boarded the 6am flight from Adelaide to Melbourne on Sunday.

Disturbingly, he does not entirely recall what happened next.

When he arrived in Melbourne, he was helped from the plane by Collingwood chief executive Gary Pert, who leapt to the three-time Olympic champion's defence on Monday claiming the alleged "assault" incident involving another male passenger had been blown out of proportion.

Hackett has not been charged, but the matter is still being investigated by police.

For so long, those close to Hackett have been prepared to back their man.

And now? Now, they're not so sure.

They are suspicious that the same dependency on prescription drugs that saw him dispatched to rehab in Arizona in early 2014 - after he was photographed walking around the foyer of Melbourne's Crown Casino looking for his missing son dressed in a singlet - is at play.

Grant Hackett (left, shirtless) at Crown Casino in 2014.

Hackett's brave comeback to the pool in the past year has been celebrated, even if he failed at the Olympic selection trials in Adelaide last week to make the team for Rio.

But there have been murmurs of him straying from the path. His statement, released on Monday amid a media firestorm over the alleged plane incident, indicated as much.

"I have stuffed up more than once and am working on these issues," he said. "It is embarrassing to hear and read the consequences of my actions."

He added: "I just have to sort a few things first so I can be as frank and open as I need to be."

It is understood he was seeking advice of doctors and also lawyers on Monday.

There is a real fear about what this latest episode could mean when it comes to the custody of his children.

Following a messy divorce from singer Candice Alley, he was forced into a drawn out battle for custody while at the same time dealing with his Stilnox dependency.

More than ever, Hackett will rely on those closest to him to get him through - but how many are willing to stand by him?

There can only be so many chances left for an athlete who has a heart of gold but appears to be battling a very real challenge of addiction.

When he boarded a Virgin flight from Adelaide to Melbourne at 6am on Sunday, the rest of his life was right there in front of him. He just had to grab it.

His swimming career was over but the respect gained from a courageous comeback, which started when the legendary Michael Phelps nudged him about getting back in the pool, was immeasurable.

He'd missed out on Australian selection yet the younger athletes were drawn to him on the pool deck, hovering and hanging off every word the Olympic legend had to say.

Hackett has a magnetic personality. Everyone loves Hacky, despite all the rough edges exposed over the past four years.

He also understands the brutal life of the professional swimmer. Having been through the wringer, and come out the other side, an official mentoring role in Rio loomed.

Meanwhile, Channel Seven was ready to pounce.

He'd done some expert commentating during the trials and whenever the viewers heard his voice, the ratings went north.

Swimming is fundamental to Seven's success in Rio.

Neither Dennis Cometti nor Bruce McAvaney will be calling the event at the Games. Hackett would've brought some serious cred to the coverage.

So impressed were the Seven execs, promos were ready to be shot on Tuesday. A contract would've been signed later this week.

Now is a great time to become involved with swimming, too.

Four years ago, the reputation of the Australian swim team was mud.

The Stilnox scandal that had ripped through the team at the London Olympics, the subsequent investigations, the mass sackings of coaches and administrators, put the sport back years.

Now, the likes of Cameron McEvoy and the Campbell sisters were cleaning up its image and giving it relevance again.

Don't worry about 35-year-old competitors. Swimming is back.

Unfortunately, when Hackett boarded that 6am flight on Sunday, he was intoxicated.

And we mean, intoxicated. Grabbing-random-man-on-the-nipple intoxicated. Getting-helped-off-the-plane-by-a-Collingwood-AFL-boss intoxicated. Fall-asleep-in-front-of-federal-police-while-sitting-in-a-wheelchair intoxicated.

(On that note, Hackett has told others he wasn't sitting in the wheelchair, but at this point it seems a minor detail).

The life Hackett was about to grab just slipped through his fingers.

There will be no official role with Swimming Australia. There will be no gig with Seven in Rio.

Almost exactly a year ago, I sat and had breakfast with Hackett at a Broadbeach cafe on the Gold Coast.

He'd just completed a dawn training session with his long-time coach, Denis Cotterell, at the Miami Aquatic Centre - the same pool where Cotterell had spotted a promising six-year-old 28 years earlier.

In light of recent events, a few comments from that interview stand out.

"Rehab is a dirty word," he said. "It was a dirty word for me before I went in there. But I needed that insight into myself."

He was also adamant that he wasn't coming back to swimming to fill a void in his life; that he needed to be staring at the black line at the bottom of the pool because life in retirement had been so problematic.

"Everyone thought when my life turned for the worst for three years there, it was because I had trouble finishing up swimming and it was all over," he says.

"That is completely false. I had a full life out of the pool. From a professional point of view, it wasn't that difficult. I was prepared. Where I did find it difficult was my personal life. I had a marriage breakdown that I can't go into too much detail about because of the court stuff.

"But those personal issues were where the challenges came from. They were where the stress came from. There were children involved. That's where the difficulties came from. Not from retiring from sport."

There are more than a few people in Australian swimming who will tell you that Hackett must now, finally, reconcile the fact that his career is over.

This is his chance to get it right. There is no other alternative.

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Andrew.webster@fairfaxmedia.com.au