Redknapp revealed that Defoe, who scored only nine times in the last club campaign, now looks sharper than ever.
He said: "Jermain did not have the best time of things last season and he had his problems with injuries.
"He scored only four league goals and he is a 16-17 goals-a-season player, no question. But he has looked fit and really sharp in pre-season.
"A lot of that is down to his own efforts because he went over to France to see a fitness coach and that seems to have helped him a great deal.
"I am definitely looking for him to have a really big season for Tottenham. He is certainly flying now."