Yamal, who took a hit to his left thigh against France, was spotted at practice with the same leg wrapped.
But de la Fuente downplayed those worries when asked repeatedly about Yamal.
"Today he participated in the training with the other teammates, and he is fine," de la Fuente said. "He is fine. He is in optimal condition."
Yamal, who was photographed as a baby alongside Lionel Messi in 2007, is considered the potential heir apparent to the title as the best player in the world. This final could be a passing-of-the-torch moment, but Yamal's coach does not want his player thinking like that.
"Lamine has to be Lamine," de la Fuente said. "Messi is and one-of-a-time-in-history player, and he's an example, a role model for youth and younger players: his attitude, his behaviour.
"At his age, he's playing such a spectacular competition at the World Cup. I insist Lamine has to be Lamine Yamal himself, and the best way we can support him is by helping him be the person we know today because he has a great potential, a great future."
Not much is making de la Fuente nervous ahead of the final except returning to New Jersey after doing a news conference and other media obligations in New York.
"I am nervous because we are going back by helicopter," he said. "I'm serious. We got here by helicopter, and we have to take the helicopter to go back and that makes me really anxious. About everything else, I'm calm."
Sixteen years removed from Spain winning the World Cup for the first time, kingpin Rodri thinks the determination of that group can be an inspiration.
But he is more focused on the individual and team development that has sparked this run to the final.
"We can even do it better," said Rodri, the 2024 Ballon d'Or winner as the best player in the world.
"I think against France, we do one of the best games we ever done as a team. But against Argentina, I think we have to rise a level because they are the champions. And I'm really confident that we can do it."
As for Argentina, Messi summed it up in a few words in what is likely to be his sixth and final World Cup.
"We will give it our all," he said. "I've said many times: we never stop fighting."
In a press conference attended by Tom Brady (American football), Novak Djokovic (tennis) and Kevin Durant (basketball) - all superstars in their respective sports - Argentina coach Lionel Scaloni was asked by the 24-times grand slam champion about the looming pressure.
"It's one more game," Scaloni said. "We cannot really think about the fact that it's a World Cup final."
No team has won back-to-back World Cups since Brazil in 1958 and 1962, and Messi now has a chance to add one more accomplishment to his already overstuffed resume.
"We've got a group of players and a group of coaches that are working incredibly hard every single day to try to bring happiness to my country," goalkeeper Emi Martinez said.
"We're going to give absolutely our best, with Leo, with the team that we have, to bring the World Cup back to my country and celebrate with our people."
