Lamine Yamal, 16, became the youngest player to represent, score and start for Spain during the international break. He came off the bench on Friday, scoring against Georgia, and then played for an hour against Cyprus on Tuesday.
In August, he also became the youngest player to start for Barça in LaLiga having previously made his first team debut in April while still 15 years old.
"He is a player that has surprised us," Deco said on Wednesday in a news conference. "[Barça coach] Xavi has always said [about him] and that is why he handed him his debut last season.
"Lamine Yamal is a kid with his feet on the ground. He has a different quality [to others]; he can contribute different things.
"We are in a situation at the club where we have a lot of young players in the team playing important roles, but he's a boy of just 16, so we have to leave him to enjoy his football. We have to support him to ensure he keeps growing in the right manner."
Deco, who was speaking at his official presentation in his new role, also confirmed Barça hope to announce a new contract for Yamal soon as a reward for his performances. Left-back Alejandro Balde, who like Yamal is represented by agent Jorge Mendes, is also in line for a new deal.
"Both renewals are on track, you will have news soon I am sure," Deco added. "They are young, important players who I am sure we will renew."
Lamine Yamal, born in 2007, joined Barça in 2014 and made his debut against Real Betis in April. He then came off the bench in Barça's LaLiga opener against Getafe this season and started their next three games before the international break, producing a player of the match performance in the 4-3 win over Villarreal.
At 16 years and 57 days old, he became the youngest player to play and score for Spain on Friday in Georgia, taking both records from teammate Gavi, before starting Tuesday's win over Cyprus in Granada.
Meanwhile, Deco says Barça boss Xavi, who he played alongside at Camp Nou, is also set to sign a new deal, with his current terms up at the end of the season.
"He has earned the right to renew," Deco said. "When it's [official], you'll know. We are happy with him, not just because of the figure of Xavi, but because of Xavi the coach.
"He happens to be one of the best players in the club's history, but he is proving himself to be a great coach with what he has done. I am sure we will reach an agreement."
Xavi took over at the end of 2021 with Barça ninth in LaLiga, steering them to a second placed finish in 2021-22 and then winning the league last year in his first full season in charge.