Sherwood knows Defoe well, having worked with him at Tottenham Hotspur, and he feels that the 32-year-old has the ability to fire the Black Cats to safety.
"If they are going to survive it's going to be Jermain Defoe who keeps them in the Premier League, that's why they forked out that sort of money for him," he said.
"He didn't have to go, he went for a lifestyle change to Canada but he still has that appetite to come back and play for Sunderland, in a relegation battle."
"Jermain can score goals on his own but he prefers people to slide the ball across the six-yard box for him to be in the right place at the right time, that's what he's done all of his career."
Despite Sherwood's glowing endorsement, Defoe hasn't actually had the impact at the Stadium of Light that many were hoping for.
The England international has only scored two goals in his first nine matches for his new club and he will determined to start improving this ratio.
Sherwood will be hoping that Defoe doesn't start finding form this weekend, though, as he takes his Villa side to the Stadium of Light on Saturday.
Villa will take a major step towards safety if they can beat Sunderland, but their task will be difficult if Defoe is on his game.
Sunderland and Villa have found goals hard to come by and it means that a clinical finisher like Defoe could be the difference between the two sides, if he shows his famously ruthless streak.