Losses to Georgia and Argentina have all but ended the Ikale Tahi's hopes of making the knockout rounds.
A bonus-point victory against the defending champions would keep alive Tonga's faint hopes of reaching the quarter finals.
Tonga are back up just five days after being battered by Argentina.
But captain Nili Latu said a few sore bodies would not stop them from giving it everything against the defending champions.
"It's something that we can't control. I think every World Cup it's always been like this but when you come up against the best team in the world, you have to be excited.
"I think our mentality has to be attack when we have the ball and on defence as well. We see that as well against Georgia and Namibia so that's something that we're going to bring into the game - try to pressure them in the set piece and just all around the field.
"That's what we need to do and we have to attack against the big teams - we can't sit back and let them have their own way and I believe that's the only way we're going to get into the game."
But even if the Tongans do produce the upset of the tournament, they'll still need Namibia to stun Argentina to sneak into the playoffs.
A win or draw with a bonus point would lift them above Georgia, though, and seal automatic qualification for the next World Cup in 2019.