Ivan Rakitic says Lionel Messi is "part of Barcelona's badge" but couldn't say for certain whether the Argentina forward will remain at the club beyond the expiry of his contract next summer.
Barca confirmed an agreement with Messi over a new four-year deal in July, but the contract has not yet been signed and doubts have set in regarding whether it will be signed at all.
In theory, if Messi doesn't sign the deal, he will be free to negotiate with other clubs from January.
President Josep Maria Bartomeu has reassured supporters there is nothing to worry about, confirming that an image rights contract and a contract with Messi's Foundation have been signed by the player's father, Jorge.
Bartomeu says it's just a matter of "protocol" and finding the right moment to sit down with Messi to have the contract signed and the photograph taken.
Rakitic says he believes Messi wants to stay at Camp Nou, despite the worries generated by the delay in signing the terms, but that he can't say 100 percent that he won't leave next summer.
"Leo's part of the club's badge," Rakitic told a news conference ahead of Wednesday's Champions League game against Juventus. "I am confident he will [stay].
"He is not just a very important player, he is more than that, looking at his career, how much he means for Barca. I can't say 100 percent if he will stay or not. That's his decision and you have to respect what each person thinks or does.
"We know the fans want to see the picture, the handshake; I do, too. I want to play with Leo tomorrow, three years, five years in the future. The only thing we can say as teammates is that we want him to stay, he has all our support and we enjoy being with him.
"From what I have read and been told, things are going well. I have confidence in the president and in Leo and I know he wants to be with us."
Barca need a point to guarantee top spot in the group and their place in the round-of-16 at the Juventus Stadium.
Standing in their way will be goalkeeper Gianluigi Buffon, who will be more desperate than ever to win the Champions League in what is set to be his last year as a professional after Italy were denied a place at the World Cup last week.
Rakitic, who will be in Russia with Croatia next summer, said it was tough to watch Buffon miss out on a spot in the finals.
"I would like to tell Buffon to go in my place because what he's done for football is incredible, simply unique," the midfielder said.
"When a child writes out his ideal lineup, Buffon is always in there. I can't explain what it's like to see him at the end of a game in that shape and to stand next to him. It's a shame he isn't able to finish his career at another World Cup and I'd honestly love to give him that opportunity.
"It's difficult to stay out of a tournament like that. When you saw him crying in the interview at the end of the match [against Sweden], you wanted to cry with him."