Xavi warned against comparing Lamine Yamal with Lionel Messi after the 16-year-old signed a new long-term contract with Barcelona on Monday.
Barça face Porto in the Champions League on Wednesday at the Estádio do Dragão, the stadium where Messi made his non-competitive debut for the Catalan club almost 20 years ago.
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However, Xavi refused to link Yamal's emergence to Messi's in 2003, pointing out that it has not worked out too well for those that have previously been compared to the Argentina forward.
"I hope Lamine can mark an era [in football], but we are not doing him any favours saying that," the Barça coach said in a news conference when asked about Messi comparisons.
"It's true the expectations are enormous and, aged 16, he is playing at a brutal level, which is hugely positive. But let's see what the future holds without comparing him with Messi. It's not gone that well for all the players that have been compared with Messi in the past."
Yamal has made nine appearances for Barça in all competitions this season and set up the winner, an own goal by Sergio Ramos, in Friday's 1-0 victory over Sevilla in LaLiga.
On Monday, he signed a new contract until 2026 -- the longest he can sign until he turns 18 -- and on Wednesday he could become the youngest player to ever score in the Champions League.
That record is currently held by Ansu Fati, who was 17 when he scored for Barça against Inter in 2019, meaning Yamal has all season to beat the mark as his birthday is not until July.
Another youngster making an impression at Barça this season is Fermín López. The 20-year-old spent last season on loan at third division Linares, but has had an impact from the bench in the Blaugrana's last two matches against Mallorca, when he scored, and Sevilla.
With Pedri and Frenkie de Jong injured, Xavi said the midfielder is ready to make his first competitive start for Barça.
"Fermín is very much part of the first team," Xavi added. "He has earned it. I like him a lot. He's been a surprise for everyone this season.
"He can help us a lot. If he believes in himself, he can be a player for this football club for a long time. He is ready to start games."
Barça won their first game in this season's Champions League 5-0 against Antwerp, while this week's opponents Porto opened with a 3-1 win over Shakhtar Donetsk.
Xavi is looking to guide Barça out of the group stage for the first time since 2020, but his side face a stern test against Porto, who lost to finalists Inter Milan in round of 16 last season.
"It's a game against a team with a coach in Sérgio Conceição who does things really well," the Barça boss said. "They are a historic opponent who have been competing well in the Champions League for years.
"They like to have the ball and physically they are strong. We have to mind the details, but when we have been brave, things have gone well. We have to be more switched on defensively."