Martin Jol is expected to oversee a major overhaul of his squad this summer.
However, one loan star he wants to stay is Cologne right-back Sascha Riether.
"Sascha is my right-back and if he's fit he will play," said Jol.
"Sascha was one of the better players this season. Of course we would like to keep him."
Jol says striker Dimitar Berbatov will also be staying: "That is not the worry I've got. He's got another year on his contract. That is not a concern at all.
"You need a lot of money to buy four or five players. If eight or nine or 10 players are leaving a club, you need at least five or six to come in.
"Hopefully we're able to do that. Otherwise we have to be very creative again."