Chelsea manager Enzo Maresca has said Premier League clubs are having to transfer academy players due to the league's profit and sustainability rules (PSR).

Chelsea have transferred a slew of players who came through their academy over the last couple of years, with midfielder Conor Gallagher the latest to be linked with an exit to Spanish side Atlético Madrid.

Gallagher, who has been at Chelsea since the age of eight, has a contract until 2025, after which he could leave the club for nothing.

With the transfer of a player developed in the academy able to be marked as pure profit on a club's books, some Premier League sides have looked at homegrown players as a source of revenue to help them limit losses.

"But this is not Chelsea's problem, this is a [Premier League] rules problem," Maresca said ahead of their preseason friendly with Real Madrid in North Carolina.

"These are the rules. For all the clubs at this moment it is almost compulsory they are compelled to sell players from the academy because of the rules. It's not only us, it's all the clubs."

Chelsea will host Manchester City in their Premier League opener on Aug. 18.