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 ($A49 million) was also reduced to 10million euros ($A16 million) 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 STG8-9million 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.
Australian Associated Press