Deportivo La Coruna defender Luisinho has said teammate Juanfran "should not be able to leave" amid continued reports of interest from Barcelona.
Barca have until the beginning of March to decide whether they want to sign a right-back to replace the injured Aleix Vidal, who will miss the rest of the season with a dislocated ankle.
Although the transfer window has closed, rules in Spain would enable them to bring in a player on an emergency basis.
"Juanfran shouldn't be able to leave, given that it would be an important loss," Luisinho said at a news conference ahead of his side's weekend game against Leganes.
"He should not be able to leave because the transfer window has closed. He's not heard anything firm, either, and is happy here. He's already rejected other offers."
Restrictions mean that anyone Barcelona move for must either already be registered to compete in the Spanish league or without a club.
Juanfran, 28, is on loan at Depor from Watford, who have an option to sign him permanently in the summer.
But Marca reported that Barca are prepared to pay the Premier League club €8 million, more than the price agreed with Depor.
Luisinho said: "I'd prefer not to imagine it. He's an important player for us and he's having a great season.
"If he has to leave, then let it be for his own good -- but we know it would be a big loss for the team."
Barca coach Luis Enrique has said the club are looking into signing a right-back and Diario Sport reported that he has had several meetings with sporting director Robert Fernandez to discuss the options.