Fiji Rugby Sevens coach Ben Ryan has conceded Jarryd Hayne is facing a monumental task to realise his Rio Olympics dream.

The league and American football convert played barely 10 minutes in Fiji's first two pool games at this weekend's Twickenham tournament, and didn't hit the scoreboard in a commanding 42-5 win over Wales.

The Pacific Island nation routed Australia 26-0 in their final pool game to secure back-to-back World Series championships.

Hayne arrived in London on Monday well down on fitness levels after walking out on his contract with the San Francisco 49ers.

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It's meant Ryan has had to nurse his latest acquisition through the opening rounds of the London tournament, making it harder to get a read on Hayne's Olympic prospects.

"His fitness is way down on our boys and that's why we're moderating what he's doing. He was pretty sore come Friday after consecutive trainings in what's been a light week for us," Ryan said.

He said he was "nowhere near a judgement" on Hayne's Olympic credentials.

"I'd be an idiot of a coach if, having played five minutes in the World Series, I can start to make assumptions on where he can go.

"He's a good footballer but we've got world class players, we're the reigning world champions," Ryan said. "When we go into the Olympic camp, there's no hiding place.

"We don't pick by face, we pick by form and he'll have six or seven weeks to prove himself. If he gets into our side because of form in seven weeks, then he's done remarkably well, and if he doesn't, it just shows the quality we've got."

Hayne has been solid enough in his limited outings for Fiji so far, but is yet to display his blistering ball-carrying ability.

"It's not about game time, it's about going out there and doing a job for the team," Hayne said. "It's all hard, continuous, I got caught in the ruck a couple of times, too. That was a good learning curve and when you're rucking and trying to ruck the ball, obviously you exert a lot of energy. It's so much faster, it's a lot quicker, [I'm] still getting used to it."

- AAP