The England striker has been sidelined for just over two months following surgery on damaged ankle ligaments.
Defoe returned to training almost a month ahead of schedule and is available to face the Gunners.
Redknapp said: "It's great to have him back. He's a fantastic goalscorer and he's different to anybody else.
"He certainly would've had six or seven goals by this stage of the season."
Tottenham have struggled for goals in Defoe's absence but Redknapp added: "The other lads - whoever's played - have done well.
"We've been lucky we've got good strikers."