Defoe played for Redknapp at West Ham, Portsmouth and Spurs and Johnson believes their relationship will be a key factor.
He said: "Why not? He's worked under Harry before, he's worked with a lot of the boys before. I worked with him for three or four years at England. He's a great lad. He's worked with Jermaine Jenas and a few of the old Tottenham boys - there are a lot of people here who could attract him to the club. When I've moved, first you look and see who you do and don't know at clubs. That has an influence on where you choose to go so hopefully Jermain will come."