Ansu Fati became the second-youngest player to feature for Barcelona in La Liga after being handed his debut in Sunday's 5-2 win over Real Betis.
"Ansu has a lot of qualities, he's quick and he uses the space well," Valverde said in a news conference after the game.
"I know he's really young. He's the youngest player I have ever given a debut to. But if we don't look at how old the other players in the squad are, we're not going to look at his age either. We look at what he can add and he's surprised us all."
After the game, Ansu, who flashed a shot narrowly wide during his cameo, remained on the pitch longer than his teammates as he took everything in.
"I was looking at my parents and my family [in the stands], all those people that have accompanied me to this point in my career," he explained to reporters.
"I stayed there on the pitch because I couldn't believe it. I wanted to enjoy that moment. The truth is that I was really nervous before, but I only have words of gratitude for everyone: the club, the manager, the supporters, who gave me a great reception."
Ansu -- who played for the U19s last season -- is younger than players like Messi and Bojan Krkic were when they made their top-flight debuts for the club, but is not the youngest player to ever turn out in the league for the Catalans.
Vicenc Martinez was 16 years and 278 days old when he made his first La Liga appearance for Barca in the 1941-42 season -- just 20 days younger than Ansu.
Following lengthy negotiations, Barcelona finally tied Ansu down to a new deal earlier this summer. The forward signed fresh terms to keep him at the club until 2022 with an option to extend the contract by an additional two years. A €100 million buyout clause was included in the contract.
Talks took longer than the club had initially expected, though, after an email made its way into the wrong hands when they were negotiating a new deal for another of the club's young stars, Ilaix Moriba.
The email, which detailed Ilaix's new deal, was sent to an employee at Espanyol instead of his agent. A source at Espanyol told ESPN FC the club were "gobsmacked" at the money on offer.
That, in turn, saw Ansu's representatives push for a better deal with Barca, especially given the interest in the youngster from some of Europe's biggest clubs.
Barcelona had always planned to give Ansu a new deal and a bumper pay rise. Along with Ilaix, he's one of the most highly-rated players currently in the academy.
The club have recently acknowledged a need to improve the terms being offered to their best young players having seen a number opt to leave for clubs like Borussia Dortmund, Manchester City and Monaco.
Ansu was born in Guinea-Bissau but moved to Catalonia at a young age and has been at the club since he was 10. He's progressed through the academy and is expected to spend this season with the B team in the Spanish third division.