The Premiership side has first option on Fernandes, who Benfica values at £7million.
Redknapp said: “I would love him to stay.
“He’s a great young player, but with Pedro Mendes and Sean Davis playing so well it has been difficult for him to get a regular place.
“I like him a lot, though. He has bags of energy, he’s young and can play. He has the potential to become a top player.
“But it is up to the clubs to get together and see if a deal can be done. I don’t honestly know what the deal is. That is up to other people here but I’d like him to stay.
“He came back into the team last week and did well against Aston Villa and he’ll likely get another chance against Everton but as for what will happen in January we will have to wait and see.”