Redknapp feels they would be able to keep the England winger at the club if there is interest from so-called bigger teams.
"Tottenham is a big club," Redknapp said.
"Man United have (Antonio) Valencia who they got in the summer so they don't need a right-winger. This is a big club.
"He's still learning the game and getting better and better. He can still keep improving.
"He is a fantastic talent but knows himself he is not the finished article. There is still a long way to go but he's getting there."