Ansu, 17, has been linked with Manchester United in recent weeks. Sources close to the Premier League side confirmed they have watched him but there is an acceptance he will remain with Barca despite rumours of a €150 million bid being made.
A source at Camp Nou told ESPN Barca have not received any concrete offers for Ansu and joked there would be a backlash against Bartomeu if the club even considered selling the Spain under-21 international.
"There has been interest in Ansu for a while from many clubs," the source said. "Even Real Madrid were monitoring him before he renewed his contract.
"It is not news to us that clubs are asking about him, but Barca will not sell. Ansu is the future of the club and if he was sold, Bartomeu may even have to go into hiding!"
Another source at the club told ESPN "however much money is being mentioned, you can ignore the speculation, even if the club lacks [money] at the moment."
Barca have been hit particularly hard financially by the coronavirus pandemic. They will have to wipe up to €200m off next season's budget and will only be able to spend money they make in player sales.
Despite that, several sources at the club all insist that Ansu will not be used as collateral to fund moves for other players.
Ansu, who was this week named among the 100 candidates to win the 2020 Golden Boy prize, has long been a target for Europe's biggest clubs, although he has courted more attention since breaking into the first team this season.
His father, Bori Fati, is still a regular at B team and U19 games -- even when his son is not playing -- where he is often accompanied by agents or scouts who want to work with him or sell him the idea of earning much more money away from Barca.
Ansu's contract, signed in December, will expire in 2022 and features a €170m buy-out clause. However, once he is permanently promoted to the first team -- he is still technically registered for the B team -- it will be automatically extended until 2024 and the clause will increase to €400m.
Sources explain that Barca have delayed triggering the extension with the hope that he may be able to feature for the B team in the third division playoffs in July.
Ansu, who was born in Guinea-Bissau but moved to Spain as a child and joined Barca in 2012, was the biggest benefactor of an injury crisis at the start of the season. He went straight from a preseason tour with the U19s in Russia -- where then-coach Victor Valdes had to buy him new boots because the ones he had "were a disaster" -- to Ernesto Valverde's first team.
He became the youngest player to represent Barca in the league since the 1940s when he came on against Real Betis in August and the club's youngest-ever goalscorer in La Liga when he scored a week later against Osasuna.
Under Quique Setien, who replaced Valverde in January, he started five games in a row in January, scoring both goals in a 2-1 win against Levante, but has fallen off the radar since. He has started just two of the club's last eight matches, with the signing of Martin Braithwaite and Luis Suarez's return to fitness increasing the competition for places.
But he remains involved with the first team and is likely to have a part to play in final 10 games of the season, starting with Leganes on Tuesday at Camp Nou, as Barca bid for a third successive league title.