Two years ago, at the London Olympics, the American was chasing Australia’s world champion James Magnussen for the gold medal in swimming’s blue-riband event.
Adrian got his fingernail on the wall first, winning by one one-hundredth of a second, the smallest possible margin in swimming.
As the gold medal was draped around his neck, it was almost as though a giant target was painted on his back, the price every swimmer pays when they go from predator to prey.
Adrian has been unable to scale those dizzy heights since London, finishing third to Magnussen at last year’s world championships in Barcelona and second to Cameron McEvoy at last month’s Pan Pacific Championships on Australia’s Gold Coast.
With three Olympic gold medals – he also won a relay in 2008 and 2012 – the 25-year-old has nothing to prove but remains committed to a sport that involves gruelling training and requires total discipline.
“My drive is just to improve, it’s not necessarily about increasing my medal count or beating this person or that person,” he told Reuters in an interview.
“I get the greatest amount of happiness from just seeing that I worked hard for something and it paid off.”
The pay off for swimmers is dubious. Standing 6ft 6in (1.98m) and weighing 227 lbs (103kg), Adrian might well have made a fortune as a basketballer or American footballer but chose a sport where there are few multi-million dollar contracts on offer and most competitors are happy just to have their university fees paid.
A few months before the London Olympics, Adrian graduated from Berkeley with an honours degree in public health.
On Friday, he was in south-east Asia, competing at the inaugural Singapore Swim Stars, an innovative meet where competitors race for cash prizes, under disco lights with pop songs blazing away in the background.
It was all in good fun and Adrian was the big winner, taking out the men’s freestyle sprint double and pocketing $20,000, a pittance perhaps for Tiger Woods or Roger Federer, but a good night’s work for most swimmers.
Adrian was a clear winner of the 100m, which was held as a one-off final, but had to dig deep to win the 50m dash, which was held over a three round shootout, with the slower swimmers dropping out until only the last two were left.
“I think there is a lot more strategy that goes into this meet… it’s about energy management,” Adrian said.
“It was tough. All the guys that swam in the 100m first were struggling to touch the wall.
“But that was a blast. That had to be some of the most fun I’ve had at a swim meet since I was a little kid.”
The exception in swimming, of course, is Michael Phelps, who has always been a team mate of Adrian on the American relays but may become one of his rivals in the future.
Since making his comeback earlier this year, Phelps has been competing in 100m freestyle and qualified, along with Adrian, for the event at next year’s world championships in Russia.
Phelps has not outlined which events he plans to swim at the 2016 Rio Olympics but if his past is any guide, he will keep his programme a closely guarded secret until he steps onto the starting blocks in Brazil.
For Adrian, the prospect of racing against Phelps holds no real fears, although he doubts it will happen, suspecting Phelps will probably choose 100m butterfly and 200m medley as his individual events – races which he won at each of the past three Olympics.
“I wouldn’t bet against him, anybody who has in the last 12 years has lost a lot of money,” Adrian told Reuters.
“It’s incredibly exciting to see him perform at a high level but I wouldn’t say he’s performing at his peak or close to it quite yet, and I think he’d be the first time to tell you that.
“If he’d had a little bit more time to train I think he’d be right on his fastest times ever, so that’s exciting to see.
“I think the 100 free is probably his auxiliary event where he will train for the 100 butterfly but the training he does for the 100 fly will translate well to the 100 free and he’ll certainly be capable of doing a good 100m free.”
Like every swimmer, Adrian has been in awe of what Phelps has done in the pool but he said he has found a new inspiration, his 17-year-old team mate Katie Ledecky, who has been ripping up the record books in women’s middle and long distance freestyle events.
“She’s incredible, just look at the way she swims,” Adrian said.
“She absolutely attacks the water and is not timid in any sense of the word.
“When she swims, she’s such a little animal and I want to be like that too.”
(Additional reporting by Yaocheng Lee; editing by Justin Palmer)