Jordi Alba implored Barcelona to come together and be "more united than ever" as the LaLiga giants battle financial difficulties.
Xavi and Blaugrana president Joan Laporta are looking to strengthen in the transfer window after finishing second in the league, some 13 points behind champions Real Madrid.
Robert Lewandowski has emerged as the main target from Bayern Munich, but doubts persist as to whether Barca can afford the Poland talisman, who has made his desire to move to Camp Nou clear.
LaLiga chief Javier Tebas suggested Barca must sell their prized assets, such as Frenkie de Jong to Manchester United, to afford Lewandowski.
Laporta hit back by insisting Tebas was intending to "harm" Barca's interests, but Blaugrana economic vice-president Eduard Romeu acknowledged sales were needed to help ease the club's worries.
Alba, speaking before Spain's Nations League clash with Czech Republic on Sunday, admitted he would like more signings but understands the situation his side is in.
"It's the situation we're in. It's not always going to be rosy. Barca would like to be in a better economic situation," he told reporters.
"We're going to go out and if we can't sign we'll have to pull from the academy, where there are very good players.
"It's the idea that the club has and I can't say more. I'd like to sign many players, but the situation is this. We have to be more united than ever, say it all behind closed doors and that's it."
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Alba, Sergi Roberto, Gerard Pique and Sergio Busquets were named as the joint captains of Barca when Lionel Messi left amid financial struggles at the start of the 2021-22 season.
On Friday, Roberto became the fourth of the captains to agree a new contract with Barca, with the other three all reportedly taking a significant drop in wages to ease the financial burden.
While Alba was delighted to see Roberto extend his stay with Xavi's team, the left-back assured the captains are committed to the project.
"There should be no doubt of our commitment to the club. I can't control what is said in the press or outside our reach, nor do I want to," Alba added.
"The needs of the club are what they are and we will be here to help. The four captains will help and I'm sure some more. We have always been committed to the club and we will continue to be.
"It's been a difficult year at club level but I'm convinced that next year will be much better."