Mauricio Pochettino has branded Manchester City's era of sustained success "a period of deception" after they were reportedly found guilty of breaking the Premier League's financial rules.
City are believed to have been found guilty of breaching the vast majority of the 115 charges brought against them.
News of the decision, reached by an independent commission, was widely reported on Friday but no official announcement has been made by the Premier League.
City have strenuously denied the charges and their chairman Khaldoon Al Mubarak on Saturday said he is still confident of proving the club's innocence.
City have won a host of trophies, including the Premier League and Champions League, since the takeover by their Abu Dhabi-based owners in 2008.
United States manager Pochettino spent seven years in the Premier League as Chelsea, Tottenham, and Southampton boss.
'MASSIVE DAMAGE TO CLUB AND LEAGUE'
The Argentine believes City's guilt has done massive damage to both the club and the Premier League as a whole.
"Whatever punishment, it's impossible to turn back time," Pochettino told reporters.
"It's done a lot of damage. Many clubs followed the rules and some didn't.
"It is a huge sadness. We get into a situation where what got celebrated wasn't that real, what seemed good maybe wasn't so good, what didn't look good maybe was good but couldn't be good because of what happened.
"We went through something where sporting fairness didn't exist. So, how do you repair everything that was damaged because of that, if it's true all of the 114 rules that were broken, we've lived through a period of deception."
The charges relate to a period from 2009-10 to 2017-18, with City also accused of failing to co-operate with Premier League investigations between December 2018 to February 2023.
APPEAL EXPECTED
City are expected to appeal against their eventual punishment, which is yet to be announced and could include a points deduction, expulsion from the Premier League or a huge fine.
There have also been calls for City to be stripped of the Premier League titles won since 2008.
Pochettino recently said Chelsea should be stripped of the 2016-17 Premier League title after being found guilty of historical rule breaches, adding that the trophy should be given to his Tottenham side, who finished runners-up that season.
But Pochettino is unsure of a fitting sanction for City.
"What are they going to do? An economic punishment? Docking points? It's really hard," he said.
"If I remember being at Southampton, then Tottenham - I remember building the Tottenham Hotspur Stadium and not having the economic possibility of a transfer for 18 months.
"Tottenham was fighting for titles with those above us and every year in the top four, getting to the semifinals of the Champions League without being able to do a transfer for 18 months, all because we needed to get used to the Premier League financial controls?
"They were so strict with us but also so lenient with others. Because of that, that's why I say: it's all very strange."