Barcelona's 16-year-old attacker Yamal has leapt into the limelight this season and established himself as a regular for La Roja on the right.
Athletic Bilbao winger Williams, 21, could start on the left flank for Spain and his stock is rising rapidly too after helping the Basque side win the Copa del Rey this season.
"They are young players, especially Lamine, he's a young boy, with incredible talent that only the chosen ones have," De la Fuente told a news conference Friday before Spain's opener in Berlin.
"They have a gift from God, very few players have these qualities."
Despite hailing the pair, De la Fuente said he was trying to keep their feet on the ground, with Yamal revealing last week he would still be doing his school homework at the tournament.
"We're trying to treat the situation normally, but also trying to explain by being humble he will develop so much more," said the coach.
"If there are bad moments things can fall away fast and there's huge criticism. That goes at his club as well.
"We're enforcing the education and training from his club. They are special footballers, Nico too, that makes them different from the rest."
However the coach said he could spring a surprise against Croatia and use Ferran Torres or Ayoze Perez instead.
"You might take it for granted that Nico and Lamine play tomorrow, you might think it's a surprise if they don't, but it wouldn't be for me," added the coach.
Yamal was not even born when Croatia captain Luka Modric made his major tournament debut at the 2006 World Cup in Germany.
"When I hear that kind of thing, I feel really old," joked Modric.
"Everyone will see him as the greatest danger for Spain, he's got great potential and a great career in front of him."
'I hope he will stop Yamal'
Yamal could be up against Manchester City defender Josko Gvardiol if coach Zlatko Dalic selects him at left-back to try and stymie the threat of the young winger.
"Josko has had a really good season at Man City, he's one of our key players," said Dalic.
"He's capable of stopping any attacker on the Spain team, he's got it all. I hope he will stop Pedri, Yamal and all the others."
Gvardiol's Manchester City team-mate Rodri Hernandez is one of Spain's leaders and said La Roja must take the tournament step by step instead of dreaming of a fourth Euros victory. Spain last lifted the trophy in 2012.
"We know the history of Euros and we're here to go after our fourth," said Rodri.
"I don't like thinking about the long term, I just want to focus on the game tomorrow."
However Rodri said Spain have proven they can beat the best and can emerge from what is dubbed the 'group of death' alongside Croatia, Italy and Albania.
"We were competitive against Brazil, we beat Italy and Croatia at the Nations League (in 2023), I think we've very hard to play against and beat.
"These tournaments come down to small moments and we need to improve in these moments."