Appointing Marcelo Bielsa as coach of Lille was a mistake, a senior figure at the French club has admitted to RMC.
Bielsa signed a two-year contract last summer and was billed as the man to return the club to the summit of French football after Lille had been taken over by ambitious new owners.
However, after a catastrophic start to the season that brought just 12 points from their opening 13 league games, leaving the club second from bottom of Ligue 1, Bielsa was suspended in mid-November and Christophe Galtier was appointed as his permanent successor in December.
After being told their fragile financial state meant they would be forbidden from making signings in the winter transfer window, the team remain in the thick of the relegation battle while Bielsa is seeking €18.6 million from the club to pay off his contract.
"We have to accept that we made mistakes. We have to say that clearly," Luis Campos, Lille's sporting advisor, said to RMC.
"The first is when the club practically gave the keys to the former coach so that he can build his own sporting project. There came a time when the club decided to give practically all the power to the former coach and in my opinion, even today as the DNCG [French football financial watchdog] said no for the winter window, that moment is going to weigh heavily on the whole season. We're going to pay very dearly for that the whole season long."
Bielsa, the former Argentina and Chile coach, was given free rein, and took the bold step of gutting last season's squad, ruthlessly jettisoning a sizeable clutch of Lille's most experienced players such as Rio Mavuba, Marko Basa and Vincent Enyeama and replacing them with young talents.
"You cannot build a team without having a spine of experienced players to support quality youngsters," Campos said. "For me, that was when the project was broken."
Campos claimed he had repeatedly told new owner Gerard Lopez that Bielsa's appointment was not the right step, and the Luxembourg millionaire, who used to own a Formula One team, now agrees.
"I've already heard Gerard Lopez say that he made a casting error," said Campos, who said he had even distanced himself from the club for three months. "He has understood it perfectly. That's why things ended as they did. It's very clear for him today that the former coach was not good for the club and the project.
"Before, everything was clear. Then things got unbelievable with a change in the project's ideas. At that moment, the president took a decision, and he accepted to let him go on his way. And I stepped back for three months."
Campos is highly respected in French football. During his spell at Monaco, he was responsible for bringing players such as Bernardo Silva, Benjamin Mendy and Tiemoue Bakayoko to the club.
He is not above making an error of judgment himself, as he admitted with Memphis Depay, who is attempting to rebuild at Lyon the reputation that was damaged by his failure to establish himself at Manchester United.
"The first time I saw Depay play, he was really very young. He was 16 or 17. I sent a message to Cristiano Ronaldo saying: 'I have found your replacement for the future,'" Campos said.
"Depay has a lot of technique, an incredible dribble, a great shot, but he lacks a competitive spirit. He hasn't developed his physical potential.
"Tactically, he's a player who can give a lot to a team, but hasn't developed at all mentally. He signed for Manchester United and his career was over. Today, he's happy to be at Lyon, but a player with his potential should be thinking of playing for Real Madrid or Barcelona. It's a question of mentality. Young players today don't have the same desire as those 10 years ago."