Townsend will return to parent club Tottenham at the end of the season.
"He'll be a top player," Redknapp said of the 21-year-old Townsend.
"He gets at people, he attacks you. They paid £10m for the left-back and he has ripped him apart. He is relentless. He just runs at you, runs at you, runs at you. He has been first-class.
"It's difficult for him back at Spurs. You've got (Aaron) Lennon and (Gareth) Bale there, so it will be hard for him to play regularly. He'll have his work cut out.
"But he'll be a good player for Spurs next year. He will go back there a better player.
"He has proved to himself what he can do. He has proved he can play in the Premier League."