Garang Kuol became Australia's youngest World Cup star on Tuesday but noted the "big difference" he must bridge in order to regularly rub shoulders with the likes of Kylian Mbappe.

Kuol, who at 18 years and 68 days old was the ninth-youngest player in the tournament's history, was brought on as a 73rd-minute substitute moments after the final goal in the Socceroos' 4-1 opening defeat to holders France.

The highly talented winger – already confirmed as a Newcastle United signing ahead of a January move – enjoyed a few bright touches yet saw a significant gap to his opponents.

Kuol did not start a single A-League game for Central Coast Mariners, although he scored six goals in 326 minutes from the bench.

Meanwhile, Mbappe was France's star man as they took the title in Russia 2018 four years ago and appears to be in the mood to repeat the feat.

"You could see the level that they're at," Kuol said afterwards.

"They're 6ft 4[in] people who are as quick as me, so there was a big difference between me and some of those players. Only hard work will get me to that level.

"I think it was a good taste to see the level the players are at. Some play in the Premier League, some play in the Champions League, so it was good to get that taste of the level."

Mbappe in particular was relentless after a slow start had seen Australia lead through Craig Goodwin in the ninth minute.

The Paris Saint-Germain forward scored the third goal before creating the fourth for Olivier Giroud, having also had a role in the second – again scored by Giroud.

Mbappe had 19 touches in the Australia box – the most by any player in a World Cup match since 1970 – and completed three dribbles.

Australia right-back Nathaniel Atkinson endured a torrid time, not helped by the introduction of attacking France left-back Theo Hernandez after his brother Lucas was injured attempting to prevent the Socceroos goal.

Atkinson was dribbled past twice and gave away possession on 12 occasions, including an error leading to France's second.

"It's obviously the first time I've come up against this type of opposition in my career," Atkinson said.

"Obviously, I've taken full responsibility for the second goal, but the beauty of the tournament is you can't dwell on it because you've got another game to fix it in three days.

"It's a good experience. It's an eye-opener. There's a reason [Mbappe] is earning 200million [Australian] dollars a year and I am where I am, but that's something to look forward to.

"It's good to come up against this calibre. You know what to work on. I know what to fix; I've played that scenario 50 times over and I could probably come up with 50 different solutions. That's football. I'm disappointed.

"It's just the physicality of the guy. The pace... it's not hidden how quick that guy is – you give him one step and he's gone.

"As a team, you can always come up with a plan, but sometimes if it's one-v-one and he gets the better of you, it's a learning curve.

"You can get your confidence up with getting a few challenges in, but there's a reason why he's one of the top three players in the world."

Australia are not giving up hope, inspired by Saudi Arabia's sensational defeat of Argentina earlier on Tuesday.

"Anything can happen," Atkinson added. "You see what Saudi did against Argentina.

"We've come up against the world champions, and there's a reason for that. They're a good footballing team. We can take confidence from the way we played early on in that game."