The agent of Momo Diame has explained the buyout clause contained in his West Ham United contract.
Diame can be signed by a rival for £3.5 million.
"The only reason some clubs have the players they have is because of a clause being inserted," said Willie McKay.
"They may make an offer that is less wages than another club has offered but because they allow a trigger clause then the player will sign with them.
"Diame was a free transfer and believed he could command a better salary than he was offered so to compensate for that the clause was put in so he could leave in six months time for £3.5million. That way the club can sell him at a quick profit or renegotiate.
"West Ham bought out Frederic Kanoute's clause and sold him for a profit; Wigan bought out Pascal Chimbonda's at £2million and sold him to Tottenham for £4.5m.
"The thing is everyone is happy with the clauses at the outset otherwise a deal would not be signed. It's only when things go wrong that people start saying they aren't happy or it's the agents' fault."