Defoe also has praised Spurs manager Jose Mourinho for bringing the best out of both of them.
He said on Mennie Talks: "Those two are the best partnership in world football at the minute.
"The hardest thing that you can do at the top level is to be consistent, so for those two to show that consistency, for me is unbelievable.
"Son is dynamic, so he runs in behind. He gets the ball and he is direct, he beats people. It's what (Pep) Guardiola did at Barcelona, he played with the false nine with Messi, with Henry on the left and Eto'o on the right.
"With Kane and Son, what Mourinho has done has been incredible.
"I think it is understanding the players that he has got. Credit to Mourinho because there were a lot of people before he took the job that were thinking "no", but I believe that you should always appreciate greatness because he is a great manager. He is unbelievable."