Tottenham boss Jose Mourinho has branded the decision to overturn Manchester City's European ban "a disgrace" while Liverpool manager Jurgen Klopp said it was not "a good day for football".
City saw their two-year expulsion from UEFA competitions lifted by Court of Arbitration for Sport on Monday, meaning they are free to compete in next season's Champions League.
Their initial fine of 30million euros was also reduced to 10million euros (just under £9million) by the CAS.
Mourinho took exception to that element of the decision, saying if they were not guilty they should not have received any punishment.
"In relation to the decision, in any case it's a disgraceful decision. If Man City is not guilty of it, to be punished by some million is a disgrace.
"If you're not guilty you're not punished. In the other way, if you're guilty you should be banned. So it's also a disgraceful decision. In any case, it's a disaster. If you're not guilty, you don't pay.
"I'm not saying Man City is guilty. I'm saying if you're not guilty you don't pay. You are not punished, even with a pound.
"I know that money is quite easy for them but it's just a principle. Why are you paying 8-9million if you are not guilty?
"If they are not guilty, the decision is a disgrace. If you are guilty the decision is also a disgrace. If you're guilty you should be banned from the competition.
"My criticism is not for Manchester City. I'm nobody to know if they're guilty or not. My criticism is for the decision."
On the future of Financial Fair Play, Mourinho added: "In this moment we are speaking about Man City. But in the past, other clubs were in a similar situation, and you know the results of it.
"So I think it's better to open the circus door, and let everybody enjoy. And go inside for free, come out, go inside again, do it with freedom."
Klopp's main gripe was the impact on FFP, which the German thinks remains important in the game.
He said: "I absolutely don't wish anybody anything bad. I'm happy that City can play in the Champions League, but I don't think it was a good day for football (on Monday) to be honest.
"I think FFP is a good idea. It's there for protecting teams and protecting competition, that was the idea from the start - so that nobody overspends and clubs before the season have to make sure that the money they want to spend is based on the right sources, let me say it like that.
"I only read a little bit about the wording (of the City case) and why it was like it was, and it's not up to me to judge these things and I don't.
"I only think this FFP frame, which is for all of us, we all should stick to. It makes sense we have these kind of rules.
"I really hope FFP stays because it gives at least kind of borders where you can go to but not over. That's good for football.
"If you start doing that nobody has to care any more at all, then the richest people or countries can do whatever they want in football. That would make the competition really difficult.
"I think that would lead automatically to kind of a world super league with 10 clubs - I don't know the clubs, but it wouldn't depend on the names of the club but on the people who own the clubs."
Meanwhile, Pep Guardiola believes Manchester City deserve an apology after successfully overturning their European ban.
The City boss has hit out at rival clubs for what he believes was a "whispering" campaign to discredit them.
City won an appeal against a two-year exclusion from European competition, imposed by UEFA for alleged Financial Fair Play breaches, at the Court of Arbitration for Sport on Monday.
Guardiola feels the club have now proved their innocence after years of accusations related to their financial strength and says it is time for others to accept their place among among the elite is merited.
"I'm incredibly happy for the decision. It shows that all that people said about the club was not true," he said.
"We should be being apologised to. If we did something wrong we would accept, absolutely, the decisions from UEFA and CAS.
"We don't expect Liverpool, Tottenham, Arsenal, Chelsea or Wolves, or all the clubs, to defend us but we have the right to defend ourselves when we believe what we have done is correct, and three independent judges said this.
"Today is a good day, yesterday was a good day for football because we play by the same rules for financial fair play as all the clubs in Europe.
"People said we were cheating and lying, and many times the presumption of innocence was not there.
"In recent years, how many times people came to our club to do this whispering on us? I would like to see these kind of people and say, 'Look in our eyes. If you have have something to say say it face to face' and go to the pitch and play on the pitch what we have to play as rivals.
"But they lost off the pitch. We can play in the Champions League because what we have done is right. That's why they have to accept it, go on the pitch and play against us there."
"I know that for elite clubs, respectful clubs, like Liverpool, Man United and especially Arsenal, it is uncomfortable us being here," added Guardiola in a robust performance at a press conference ostensibly to preview City's Premier League game against Bournemouth on Wednesday.
"But they have to understand we deserve to be here. If we want to compete with them, we go on the pitch and compete with them and try to achieve what they have achieved in the past, decades ago, and what we have done this decade. We deserve to be stronger year by year.
"Sometimes we win, sometimes we don't but they have to understand it. If you don't agree, knock on the door or our chairman and CEO and talk. Don't go from behind whisper, seven, eight, nine clubs - go and do it on the pitch.
"We are not banned because we follow the rules for the Financial Fair Play and the rules UEFA and FIFA had decided. We have done it properly in the right way. People have to understand, right now, that we are here."
Guardiola also hit out at Javier Tebas, the president of LaLiga, who claimed CAS was "not up to standard" following the ruling.
He said: "Senor Tebas must be so jealous of the Premier League and English football.
"He's an incredible legal expert, from what I see. Maybe next time I'm going to ask him in which court and which judges (we) have to go to."
Guardiola, who has one year remaining on his contract, was asked about his own long-term future in light of the CAS ruling.
He said: "Now is not the time. I have one more year. One year for a manager is a long, long time and the decisions we thought to do before the sentence, it was quite similar now.
"But my personal situation was clear, because I said months ago, I would have stayed here (next year). It doesn't matter if we were in the Champions League.
"Some people here in England suggested we should play in League Two, so I would have stayed here."