The Black Cats have started this season in dire form and are still without a Premier League win, leaving them propping up the table as things stand.
Although there is plenty of time for them to recover the ground that they have lost, Defoe acknowledges that the North East outfit have to start picking up points if they are to steer clear of trouble.
"It is a big game, even more so because of how it has gone the last few games,” the experienced striker said. “We’ve not had that luck and not reached those levels we reached in the closing stages of last year, so it is a massive game and it is a game we need to win.
“We need points now and as players we understand that; everyone is trying and I think we just have to approach it like any other game, don’t get too tense and try to relax.
“It is a long season and there are so many more games to play, but it is important that we start getting points now because you can’t wait and think we will do it next week, we will do it next week – we have to do it now."
Sunderland have looked disjointed throughout the campaign so far, with their attack and defence not functioning as intended.
The Black Cats have conceded more times than any other side in the Premier League, while they only have seven goals to their name.
A porous defence and an impotent strike force is never a formula for success, and West Ham are not the side an out-of-form team would pick to face at this stage.
The Hammers are flying high in the Premier League, and have already beaten Manchester City, Liverpool and Arsenal on their travels, meaning they will visit the Stadium of Light full of confidence.