Professional Footballers' Association chief Gordon Taylor says it will be "practically impossible" for Luis Suarez to leave Liverpool this month.
Suarez, 26, has been told to train alone after seeking a move to Arsenal.
"With the transfer window expiring, the difficulties of not only selling him to a competitor but also replacing him makes it practically impossible," Taylor said.
Liverpool owner John W Henry has said Suarez will not be sold this summer.
Arsenal have had two offers turned down by the Reds, the latest of which was a pound over £40m.
Uruguay international striker Suarez thought this offer would trigger a clause a his contract, allowing him to move.
"I think it really muddies the waters to have buy-out clauses that are supposed to be confidential between employer and employee," Taylor told BBC Sport.
"Inevitably that gets out. The drafting of such clauses are far from straightforward.
"These are issues we are going to have to raise with the Premier League at our regular discussions."
With less than four weeks to go before the transfer window closes, Henry is adamant any offers from overseas clubs will also be rejected.
"Suarez won't be sold, even if a foreign club comes in, because we do not have time to sign a suitable replacement," Henry said.
The American revealed that Suarez and his agent, Pere Guardiola, were informed any deal for him to leave Anfield would have to be completed early in the transfer window - giving manager Brendan Rodgers sufficient time to reinvest the fee.
Rodgers has said the player has shown "total disrespect" for Liverpool and, when queried whether he envisaged the Uruguay international turning out for the Reds again, Henry replied: "That's going to be between the manager and player.
"The manager is upset, as he should be. The supporters are upset, Luis is, but that's going to be between those two and his team-mates. We need Luis. Hopefully this will pass."