The striker has been sensational for Sunderland this year.
The Sunderland striker has been in sensational form for the Black Cats this season with 18 goals in all competitions.
15 of those goals have come in the Premier League and have played a huge part in keeping his side in with a chance of survival this season.
He was important once again at the weekend as he scored the winning goal in a vital 3-2 win over Chelsea.
A victory over Everton in midweek will see Sunderland secure their Premier League status, and if they do that, Redknapp says Defoe could be viewed as one of their most important players.
“He might not win any big awards but you'd do well to find a player who has been more valuable to his side this season than Defoe,” he told the Daily Mail.
“As soon as he took that touch in the box you just knew he would score. If he keeps them up he could be one of the most important players in the club's history.”
Defoe will now be hoping his fine form across the season has convinced England manager Roy Hodgson to give him a chance this summer.
The Three Lions boss is yet to name his squad for Euro 2016 in France and even though he has plenty of options up front, Defoe could be among them.
He would add some much needed experience to a young squad, and with Arsenal's Danny Welbeck looking likely to miss out, Defoe could be in with a chance of making it.