"Normally, the loser buys the Cokes. I'd say it's about 50-50 between us."
"50-50? He doesn't score at all!"
So it goes between New Zealand 2015's top scorer and the tournament's only unbeaten keeper. Viktor Kovalenko and Bohdan Sarnavskyi, friends and team-mates with Ukraine and Shakhtar Donetsk, are discussing their duels during free-kick practice in training. And the former's success rate is causing some debate.
Sarnavskyi is the first to soften. "Viktor is very good at free-kicks, so he gets a few past me," the keeper says of Ukraine's star forward, scorer of a superb set piece in the 3-0 win over USA. "I don't make it easy for him, but he's a great player."
Kovalenko's class has been evident in all three of Ukraine's matches, and in every one of his five goals thus far. But the full extent of his potential was revealed by the scintillating second-half hat-trick that undid the Americans, taking Ukraine through as Group A winners.
"You wouldn't know to see him on the field that he's a year younger than everyone else in the team," said Sarnavskyi. "He is much stronger than most of the players in this tournament and I'm sure that won't be his last hat-trick at a World Cup."
Ukraine's coach, Oleksandr Petrakov, had been prepared to go further still. Spurning the traditional tactic of relieving pressure on young players by playing down any hype, he made clear his expectations for Kovalenko. "Am I surprised he is top scorer? Not at all," said Petrakov. "He should be top scorer and he should finish the tournament as top scorer. And I'm sure he will."
Quite a statement. And yet, when informed of this prediction, Sarnavskyi didn't bat an eyelid. "I agree with the coach," came his deadpan reply. "In fact, I'm pretty confident about it."
Back home, we have an expression that says, 'What soldier doesn't want to be a general?' That counts for us here.
As for Kovalenko himself, the swagger with which he plays is nowhere to be seen in his off-field demeanour. But amid the youthful shyness, there is a steely determination not to become distracted by targets he perceives to be essentially selfish.
"Honestly, I'm not even thinking about that," he said of the top-scorer race. "Personal awards should always be secondary in a team sport. My only ambition is for Ukraine. I want us to reach the final."
Few would have envisaged that being a realistic target before this tournament kicked off. However, the eastern Europeans' performances have led to a reassessment of the team's potential, and Sarnavskyi shares his team-mate's ambition.
"Back home, we have an expression that says, 'What soldier doesn't want to be a general?' That counts for us here. We don't want to be just another team at this tournament."
If Ukraine are winning the battle to achieve something extraordinary, it is not solely due to Kovalenko's goalscoring. At the other end of the field, Sarnavskyi has lived up to his reputation as one of his position's rising stars, emerging from the group phase having registered three clean sheets and one superb penalty save.
"He's a good friend of mine, but anyone can see that he is a great keeper," Kovalenko said. "To have kept a clean sheet in every match - how can we ask anything more?"
But just as Ukraine's talented forward is resisting the desire to chase the top-scorer award, so their equally impressive keeper is unmoved by talk of the tournament's goalkeeping equivalent: the adidas Golden Glove.
"It would be nice, but I'm not here for that trophy," he said. "If my team wins the World Cup and another goalkeeper gets that award, I definitely won't be disappointed.
"I'm very happy we're the only team not have to conceded here, but that is a great achievement which is not only mine. As for saving the penalty, let's just say I have my secrets. I also saved one in the European Championship last year, so I suppose I'm doing something right."
Neither overplays the issue, but it is also true that Kovalenko and Sarnavskyi have the most compelling source of motivation. The ongoing conflict in Ukraine, which has forced the Shakhtar duo to relocate to Kiev, has taken a heavy toll on everyone in their squad and throughout their home country. If they are chasing a place in the final, it is - as Petrakov told FIFA.com before the tournament - for a simple reason. "We owe it to all the people back home."
"We definitely feel the same," was Sarnavskyi's response. "The main satisfaction in what we've done so far has been making our people happy."
Thanks to those group-stage successes, Ukraine's U-20s are already guaranteed a warm reception when they arrive home. But with Kovalenko's goals and Sarnavskyi's saves propelling their medal quest, don't bet on them making that return journey any time soon.