Messi's future has been the subject of fresh speculation since last week's humiliating 8-2 Champions League quarter-final defeat to Bayern Munich.
Reports in Catalonia suggest the six-time Ballon d'Or winner is still lukewarm over the prospect of remaining at Camp Nou following a meeting with newly installed head coach Ronald Koeman.
Koeman succeeded the ill-fated Quique Setien and Eric Abidal has also moved on from his post as sporting director.
Speaking to Mundo Deportivo, ex-Porto playmaker Deco urged Barca to get their house in order or face up to an unpalatable reality.
"I don't know [if Messi will leave], but he has a contract," he said.
"He is a player who wants to keep winning and it will depend on what Barca does when it comes to offering him a competitive team. I haven't spoken to him, but I'm sure that's what he thinks.
"I think he has to think about his future at a sporting level. It is very difficult to make a decision because we are talking about the club of his life; it is not that he has been at Barca for three or four years.
"We are talking about the best player in the history of the club and his family is linked to the city. It's not easy.
"But it is also clear that he wants to keep winning. We cannot imagine a Barca without Leo, but it can happen."
Whatever Messi decides upon for his next move, Deco does at least feel the under-fire Barcelona board have happened upon a safe pair of hands in Koeman.
"He is a coach who knows the club very well and has a lot of experience," he added.
"He knows the whole Barca environment and I think he can help Barca at this time."
The 21-year-old has been a mainstay of Barcelona's team this season, starting 11 of their 13 matches in LaLiga and all four Champions League games, after a difficult campaign last year.
Pedri missed a total of 25 games for club and country with injury problems last term, including the semi-final and final of Euro 2024, having been forced off after eight minutes during Spain's quarter-final victory over hosts Germany.
His fitness has been a big question for a number of years, having suffered from hamstring injuries since 2021, following the 2020-21 season in which he played 73 matches for club and country.
But with injury problems having dissipated, Deco is excited at the prospect of having him in the team long-term.
”To go for a renewal the first thing you have to know is what the players are looking for, and I think they are looking to win titles, be in a competitive team and, of course, have good contracts," he told Mundo Deportivo.
"I thought that way and I think we have players who also think that way. I think Pedri’s renewal will happen because I think Pedri wants to make history at the club."
Pedri has been at Barcelona since joining from Las Palmas as a 17-year-old in 2020. Deco is confident that it feels like home for him now.
"He feels comfortable here, he is happy, he wants to win titles, he is back at his best after working hard, understanding that there was work behind him that he had to do after so many years of suffering a lot with many games and injuries," he said.
"He has understood it and has seen that he had to work in a different way, improve, and he was on time. We will do the renewal. He has this season and another one left.
"We are focused on winning important things this season, but also on guaranteeing the future of important players and Pedri is one of them.”
Deco affirmed the club’s faith in current number nine Robert Lewandowski, who is in form with 14 goals and two assists after 13 games in LaLiga this season.
Gyokeres, by comparison, has 16 goals and one assist in the Primeira Liga while, despite a dip in form, Erling Haaland has 12 goals in the Premier League this season.
Barcelona, however, are “happy” with Lewandowski and hope he will lead the line in the Catalonian capital for another season at least.
"First we have to know whether Haaland is what we want for the future. We don't know that now,” Deco told El Mundo Deportivo.
"At the moment we don't want any 'nine.' We have Robert. We are not planning anything with any 'nine.' It's not a priority because we have to focus on this season."
Lewandowski leads the Barcelona squad for shots (38) and shots on target (26) in the league, indicating the 36-year-old is still maintaining pace at the top level.
He leads the league for goals with Real Madrid’s Vinicius Junior coming closest to matching his tally, trailing by six goals.
"I think it's very difficult to find a striker like Robert nowadays. There are one or two of this level. Maybe Haaland or another one. There are not so many of this level available,” explained Deco.
"But we are not going to get hung up on finding any striker now because we are going to focus first on what Robert can do. I surely think he is happy to be here. He is a winner and if we have a big season I think he will want to stay.
"We want Robert to continue to be happy, to score goals and to stay at least one more season."
While the Pole is without a goal in two games, Barcelona’s rumoured target Gyokeres has not faltered.
The Swede caught global attention in Sporting CP’s recent Champions League clash with Manchester City, producing a hat-trick to help his team to a shock 4-1 win.
He accumulated an expected goals (xG) total of 2.41 in the match, accounting for most of Sporting's overall 2.87xG.
"Gyokeres is a good player. He has been scoring goals for some time in Portugal. We know him as we know others, but it's not a priority for us right now,” said Deco.
"When the time comes to make a decision and I have to make it because I am the one at the club, we will consider the options. But I don't think it's the right time to talk about any player."
