Derby County are chasing compo from Tyrone Mears over his move to Olympique Marseille.
The Daily Mail says Mears has received a legal letter from Derby demanding £75,000 after the Championship club claimed he flew to the south of France for a two-day trial without permission.
Mick McGuire, the PFA deputy chief executive, said: "Derby are entitled to fine him that amount because he is still on a Premier League contract. We don't know if he will appeal."