Real Madrid goalkeeper Iker Casillas insists he would welcome the arrival of David de Gea at the Bernebeu.
Relegated Hull have released longest serving players Paul McShane and Liam Rosenior as they reshape their squad.
Steve Bruce believes Hull's promotion prospects rest with what happens to his loan stars.
The Tigers moved level on points with npower Championship leaders Cardiff after beating Derby 2-1 at Pride Park.
Goalkeeper David Stockdale returned to Fulham this week and playmaker David Meyler will now go back to Sunderland.
Manchester United duo Ben Amos and Robbie Brady and Sunderland's Ahmed Elmohamady remain with the Tigers until the new year.
Bruce hopes he can keep them all at the KC Stadium until at least the end of the campaign as he sees them as pivotal to the Tigers' chances of returning to the Barclays Premier League.
"I don't want to have to make too many changes to the squad so I hope we can keep them," said Bruce.
"I want to keep them all. Hopefully we can keep the group together and secure the loan deals until the end of the season, or even make some of them permanent.
"But it's a difficult time in January so we will have to wait and see."