The 18-year-old, who this week made his full Portugal debut, has been linked with a host of top clubs, including Manchester United and Real Madrid
Sporting C.P. defender Nuno Mendes has been backed to make a big-money move this summer having been dubbed the top talent in Portuguese football.
The 18-year-old only made his first-team bow in June, but he has enjoyed a rapid rise, which culminated in him making his international debut as a starter in Portugal's World Cup qualifier against Azerbaijan on Wednesday.
Manchester United, Liverpool and Real Madrid have all been linked with the teenager, and it seems only a matter of time before he leaves the Primeira Liga leaders behind.
What was said?
Speaking to Goal after Mendes was named on the 2021 NXGN list of the world's top teenage footballers, former Portugal international Costinha said of his compatriot: "Nuno Mendes [is the top talent]. I don't think he will be here next season.
"If I was a scout for the big clubs in Europe, I would look at him. Eighteen-years-old, a left-back – and there aren't many left-backs in the world with that quality – then I would definitely go and pick him.
"He is strong physically and in his head. He has an excellent left foot and he has very good pace.
"Sometimes, I think he needs to learn more about defending, but he is only 18. He has so much time to improve.
"I don't think he is going to stay here for a long time."
Nuno Mendes: The story so far
Mendes joined Sporting's academy at the age of 10, after the Lisbon outfit were forced to fight off interest from rivals Benfica and Porto in the precociously talented youngster.
Originally deployed as either a No.10 or wide forward, he was eventually moved to full-back, though his attacking instincts make him more suited to his current role as a wing-back.
He was called up to Ruben Amorim's squad following the coronavirus-enforced suspension of football last spring, and made his debut off the bench in the Leoes' second game back in the early summer.
The following week, he became the youngest player since Cristiano Ronaldo to start a match for Sporting, before becoming the club's third-youngest scorer, behind only Ronaldo and Ricardo Quaresma, in October.
With his displays having caught the eye of Europe's elite teams, Sporting have twice improved his contract in the last nine months, and the latest deal he signed in December included a €70 million (£60m/$82.5m) release clause.
Who are Portugal's other NXGN stars?
Mendes is one of four Portuguese players on the 2021 men's list, and one of three currently at Sporting.
The highest-placed of his compatriots is Fabio Silva, the striker who left Porto for Wolves in a club-record £35m ($47m) in September, who ranks at 17th.
Mendes places 23rd, while his Sporting team-mates, Eduardo Quaresma and Joelson Fernandes, come in 36th and 44th, respectively.
Centre-back Quaresma has been linked with Manchester United and Atletico Madrid in the past, while winger Joelson and fellow teenage forward at Sporting, Tiago Tomas, have both reportedly appeared on Arsenal's radar.
And Costinha has been keeping a keen eye on the talent coming through in the country in his role as a prominent pundit.
"Quaresma hasn't been getting as much time in the team as Goncalo Inacio, who is doing very, very well," the ex-Porto man said.
"I think the striker from Sporting, Tiago Tomas, is very good. He has pace, but he needs to improve some qualities as a striker in receiving the ball with his back to goal. These are small things with training that he can improve.
"Portugal will always have excellent young players. We maybe need to give them more space in the first team and be less afraid to put them in, even if we lose games.
"But, I repeat, the one I see who won't stay here next season is Nuno Mendes. He is a very good player."