The 24-year-old Croatia midfielder has been linked with a move to Manchester United in recent days.
“He’s not a player we should even be thinking about selling or want to sell,” said Redknapp.
“I don’t think that will be a problem keeping him here.
“I don’t know what his contract situation is at the club but I’m sure he’s happy here.
“He’s a fantastic player and I want to keep my best players.”
