Barcelona brought on 15-year-old forward Lamine Yamal in their 4-0 win over Real Betis on Saturday to make him their youngest ever player in LaLiga.
The Catalan club said he was their second youngest player of all time, behind Albert Almasque in 1902 who played in the Macaya cup at 13 years, 11 months and six days old.
The winger replaced Gavi with four minutes plus stoppage time remaining to make his debut at 15 years, nine months and 16 days old.
"He's got innate talent in the final third which is difficult to find," Xavi told reporters.
"He doesn't seem like he's 15 years old, he's more mature than his years. I've seen him train and he's showed it.
"He played 10 minutes, but did well, he can mark an era at the club."
Yamal had a shot on target during a bright cameo as Barcelona restored their 11 point lead at the top of the table.
Xavi agreed with comparisons to Lionel Messi and Ansu Fati, who also make their debuts at young ages for the club.
"I told him to try things and he did," Xavi told Movistar.
"At 15 years old, just imagine it. He's a special player, he could score, assist, he had confidence.
"When you see it in training you realise he could be big."
Yamal also created a chance for Ousmane Dembele with a scooped pass over the top for the French winger.
Raphinha, who scored Barcelona's third goal against Betis, said the squad were all talking about Yamal's debut.
"We were talking about this on the bench, when I was 15 I think I was playing for my neighbourhood team," Barca winger Raphinha told Movistar.
"And seeing him come on in this stadium, with all these people, is incredible.
"It would have been better if he scored, but he will score at a better moment and he will be very important for the club."