Redknapp told the Daily Star: "I don't know the answer to that to be honest.
"I think he must have a buyout clause. I would imagine he has a buyout clause but I don't know how much."
Redknapp, whose side have already booked a spot in the Championship play-offs, added: "Someone said Everton were in for in for him too.
"But I don't even know what the deal is or what his buyout clause is."
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