Johnson told The Mirror: "We don't need to speak how big the club is, the club's massive. It's got massive backing, the chairman's been fantastic, it'll be great to give him something back.
"Jermain has worked under [manager] Harry [Redknapp] 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 few of the old Tottenham boys and there are a lot of people here who could attract him to the club.
"Yeah of course, I think when I've moved to clubs first you look and see who you do and don't know at clubs. I think that has an influence on where you choose to go in the end, so fingers crossed and hopefully Jermain will come."
Defoe's pre-season preparations suffered a blow last weekend, as he was forced off after just eight minutes against Monaco with a hamstring strain.