According to Sky Sports reporter Kaveh Solhekol. PFA (England Professional Players Union) contacted Chelsea to ensure that Sterling and DiSassi were treated properly.
PFA has contacted Chelsea to ensure that Sterling and DiSassi are treated in compliance with FIFA regulations. The two players are currently excluded from first-team training after failing to leave the team this summer. Chelsea is working closely with the PFA, and the two players are also training regularly, and as part of the program, they are equipped with a full-time coach. Chelsea will try to find new owners for them as the winter window opens.
Article 14(b) of the FIFA Player Identity and Transfer Regulations stipulates that if a club isolates players from the team, allows them to train alone (or restricts them from entering first-team environments - such as locker rooms, canteens, physiotherapy rooms, etc.), it may constitute a "abuse" of the club, and the player has the right to seek termination of the contract and issue notices on "legitimate reasons".
However, the situation is more complicated, because being a free agent is not necessarily good for the player – especially if they have a high-paying contract. This is a problem that PFA closely monitors in professional football events of all levels. Their overall approach is to make sure the club is aware of the rules and work with all parties to find solutions.