The 29-year-old Brazil international moved to the Nou Camp from Liverpool in 2018 in a £142 million ($192 million) deal but struggled to establish himself and spent the 2019/20 season on loan at Bayern Munich.
A tearful Aguero, who had a health scare in Barcelona's match against Alaves on 30 October, said at a press conference at Camp Nou that he had decided to stop playing.
Hazard has endured a nightmare two years riddled with injuries since joining from Chelsea for 100 million euros ($115.9 million) and he stayed on the bench during Madrid's 2-1 win over Barcelona at Camp Nou on Sunday.
"I don't think there is a solution," said Koeman in a press conference on Tuesday. "For me it's a social problem, they are people who have an education problem, they don't know what morals and values are."
Fati, who has recently returned after almost a year out with a knee injury, will have a release clause in his new deal set at one billion euros.
Josep Bartomeu said that most of the club’s financial woes had been caused by the impact of the pandemic, which closed down Camp Nou for more than a year and reduced other sources of revenue.
The measure comes at a time when COVID-19 cases in Spain have dropped to their lowest level since July 2020.
Barcelona want to increase Camp Nou's capacity to 110,000 while also refurbishing its surrounding area, which includes a pavilion for the club's other sports, the museum and stores.
The club lost star player Messi to Paris Saint-Germain this month because it could not give him a new contract that would fit within the Spanish league’s strict financial fair-play regulations.
LaLiga: Barcelona edge closer to top spot after Ousmane Dembele's late winner against Real Valladolid
Victory makes it six in a row for them in LaLiga, another win – particularly after an unconvincing performance – enhancing the sense that momentum now lies with Atletico's rivals.
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The operation comes less than a week before presidential elections are to be held at the club.
Flags at the Camp Nou flew at half mast, Maradona's image was displayed on every screen and digital advertising hoardings while a club official held a framed Maradona Barcelona shirt.
“Not having fans is the worst thing that can happen in a Barça-Madrid match,” Barcelona boss Koeman said.
LaLiga: Barcelona coach Ronald Koeman says no concern about Lionel Messi despite attacking club over Luis Suarez's exit
Koeman was also keen to point out it was not solely his decision to let Suarez join Atletico Madrid, with the Dutchman insisting he is not the "bad guy in the movie".
Barcelona hopeful Lionel Messi will stay with club as they try avoid abrupt end to player's career at Camp Nou
A day after the Lionel Messi told the club he wants to leave, Barcelona said their restructuring project still revolves around the player.
Barcelona led the league by two points over Madrid when the league was stopped in mid-March for three months while Spain’s reined in its coronavirus outbreak.
Champions League: Barcelona coach Quique Setien wants UEFA to schedule return leg of last-16 tie against Napoli in Camp Nou
Barcelona drew 1-1 at Napoli at a full and rocking San Paolo stadium but the second leg was postponed due to the COVID-19 pandemic and the match is one of four ties that still need to be settled before the quarter-finals can begin.
Vissel Kobe's Andres Iniesta plots a return to Barcelona, where beauty, magic and grace appear to have evaporated
From 6,500 miles away, Andrés Iniesta has been contemplating his return. He doesn’t know when it will be, or under what circumstances, but he is sure he wants to go back to FC Barcelona