Arturo Vidal said Barcelona have to "change a lot of things" as their DNA is being left behind amid the club's crisis, which could see Lionel Messi sensationally leave.
Messi has handed in a transfer request and the Barca captain is reportedly wanted by Pep Guardiola's Manchester City in the Premier League, while Paris Saint-Germain, Inter and Juventus have also been linked.
It comes after Barca were dethroned by bitter rivals Real Madrid in LaLiga and humiliated 8-2 by Bayern Munich in the 2019-20 Champions League quarter-finals, with Ronald Koeman replacing Quique Setien – who was only appointed head coach in January.
And Barca midfielder Vidal has called on the embattled side to change their mindset as pressure mounts on president Josep Maria Bartomeu.
"Barcelona have done things that don't fit with a team at the top level," Vidal said in an interview with Daniel Habif via Youtube.
"In the end, you realise this when you face an organised team, a team that has a winning mentality, with players that are physically prepared and that has a very strong game plan.
"That takes its toll when you're weak in the head and in energy - that happened to us. Barcelona first have to change the way they think because football has evolved a lot.
"DNA is being left behind and other teams are improving in other aspects. Nowadays, football is more physical, more about strength and speed, and technical ability can sometimes come second. Barcelona have to change lots of things.
"A club, which I think is the best in the world, can't have 13 professional players and the rest youngsters.
"Not because they don't deserve to be there, but they have to be competing with the best and with who has to play.
"Every club has 23 players fighting for a place, improving and getting better every day. But when they don't progress, when you think you can always win with your DNA, that's when you're mistaken."
"There are lots of good players. We have Messi, who is the number one and is an alien, but he needs help," Vidal added. "He needs players that improve the team and that get better results."
Vidal's future at Camp Nou is far from certain amid links to Serie A champions Juve and Antonio Conte's Inter.
Chile international Vidal won four league titles during his time at Juve – three of those under head coach Conte before eventually joining Bayern Munich in 2015.
"Conte is like a machine, he is tactically the best," Vidal said. "As for my future, I'm relaxed, we'll see what happens. I am very fond of Barcelona, but we'll see."
Former Juve team-mate Andrea Pirlo is now coach of the Turin giants after replacing Maurizio Sarri, and Vidal added: "It's spectacular that he has become the coach of Juventus.
"If he was incredible as a player, imagine him as a coach. He has a real vision of the sport that very few have ever had in football, so I think he can do really well.
"Pirlo is also a wonderful person too, so I can only imagine he’ll be a great coach. We spent four years together and won the Scudetto four times, so if he were to call me, I'd be happy."