“I just want to win, that’s all,” he added. “Everything else is just noise. I’d be a liar if I said I didn’t feel any pressure but it doesn’t eat away at me. I let it ooze into my body and I use it as nutrition. It fuels me.”

The United States team are looking to Chase Kalisz and Jay Litherland, although neither have posted times fast enough to suggest they can ambush Hagino.

Hagino’s Japan team-mate Daiya Seto, who won last year’s world title in Hagino’s absence through injury, also poses a threat while Brazilian Thiago Pereira, the London silver medallist, will have feverish home support.

But Hagino believes he is in the shape of his life.

“I’m in race shape, my body feels pumped up,” smiled Hagino ahead of what could be the ‘amuse bouche’ before he attempts to usher his hero Phelps into retirement in the 200m medley – an event Phelps won at the past three Olympics – later in the week.

“I’ve been ready for a few days, so I’m not worrying,” added the Japanese hotshot, bidding to become the first non-American to win the Olympic title in the men’s 400 medley since Hungary’s Tamas Darnyi at the 1988 Seoul Games.

“I’m in the best shape of my career. I’m swimming better than ever day after day and that’s giving me great confidence. I’m ready to go.”

Hagino, also a decent bet to win a medal in the 200m freestyle and 4x200m freestyle relay, insisted he was a stronger competitor since missing last year’s world championships after breaking his elbow in a cycling accident.

“It’s been a real rollercoaster ride, no question,” he said. “I couldn’t even straighten my arm because of the injury.

“A lot has happened, but if there hadn’t been that drama I wouldn’t be here feeling this confidence two days before the start of the Olympics. It’s all part of life and it’s definitely made me stronger.”