The Black Cats sit at the foot of the table and are yet to pick up a win this season and this weekend they make their first visit to the Hammers new home the London Stadium.
Defoe is looking for Sunderland to increase the pressure on a West Ham side who have struggled, particularly at their new home, this season.
He told the club's website: "You could say they have gone backwards a little bit from last season.
"They've not started this time like they did last year but if you look at the great individual players they have got, they can create things out of nothing.
"It's important to go there disciplined, believing we can win that game.
"For West Ham, playing in their new stadium, the pressure is on them and we can use that to our advantage."
Defoe wants the side to cut out the errors they have been making, he added: "When the ball is at the edge of your box, just be disciplined, kick it away, it's not difficult.
"We are trying to play one-twos on the edge of our own box, it's a schoolboy error."