Rafael Benitez and Arsene Wenger have expressed their doubts over the Premier League's plan to introduce a quota system for home-grown players.
Liverpool manager Benitez will take charge of his 300th match since joining the Reds as another Champions League campaign starts tomorrow with a Group E clash against Hungarian champions Debrecen at Anfield.
He has had to contend with quotas in European football for several years, but now he fears for the overall quality of the English game.
The new regulations mean there will have to be eight home-grown players in every 25-man league squad from next season. The 20 Premier League clubs met last Thursday to agree the introduction of the rule.
Benitez said: "Maybe it has been brought in too soon. In the Champions League we had two or three years to increase the numbers of ome-grown players. The problem in England is that there is a big gap between the academies and the first team, the reserve league is not filling this gap.
"It may now be difficult to maintain quality, but we will continue to do our best. The number of players is not the point, the quality is the point. But if they have decided this maybe they have been thinking about this rule for a long time.''
Benitez added: "Similar rules have been introduced in the Champions League, first four, then six now eight home-grown players in each squad. We were all given three years to make these changes slowly. Now it will be different, and quicker. It all depends on the players. Not the amount, more the quality.
"If a top side has to find eight players from the academy straight away, it may well be difficult. Academies do not produce too many in England, (home-grown) players tend to play in the lower divisions because they may not be good enough for the very top.
"Clubs have to bring in the best young players from around the world at a young age to produce the quality (in the academies), and we have been expecting some sort of rule change like this. People talk too much about the age of players and where they are from. They forget about quality, the Premier League is the best league in the world because of the quality, not because of where the players come from.
"When they decided to put this rule in place, maybe they have been thinking about it for years. Sooner rather than later, with the Champions League rules changing, we expected something similar here. Players like Michael Owen, Wayne Rooney and Steven Gerrard - when they were 17 - were playing in the first teams. But not too many, because the level is too high.
"Most players need time. But between 18 and 21 years of age, the reserve league is not good enough for them. In two or three years' time we will see what the quality of the league is like then.''
Liverpool have one of the highest numbers of foreign players in the country, and can only just manage to meet the current Champions League criteria of eight home-grown players in a 28-man squad.
The likes of Stephen Darby, Jay Spearing, David Martin, Martin Kelly, David Amoo and Nathan Eccleston are academy players in the Champions League squad, but none are close to Premier League level yet.
Arsenal manager Arsene Wenger tonight rejected the new rules "artificial''.
Speaking in Belgium ahead of Wednesday night's Champions League Group H opener against Standard Liege, Wenger declared: "I am not in favour of it, and I said that many times.
"I feel that when you want to see the best players in the best league in the world, you have to be open. To accept competition - and we live for competition - it is not to accept artificial rules and that is why I am against it.''
Wenger's stance is in contradiction to Minister for Sport Gerry Sutcliffe, who welcomed the moves by the Premier League as being good for the long-term health of football.
"These moves will encourage clubs to develop and bring through young talent and help ensure clubs are financially stable,'' Sutcliffe said. "Clubs that do not pass the test may find themselves blocked by the Premier League from making new signings and have to agree a new budget.''