Global players' union Fifpro are reportedly keeping an eye on Barcelona's treatment of Frenkie de Jong amid the club's salary row with the midfielder.
Barca want to sell De Jong this summer - with Manchester United desperate to sign him - but he is not prepared to leave until the dispute is settled.
The Dutch international is owed £17million in wages by the Spanish club, which he agreed to defer to help the club's finances during the coronavirus pandemic.
According to The Times, insiders at Fifpro have confirmed that they are monitoring the situation closely but 'such situations happen "all the time" with clubs and are symptomatic of a failing system'.