If we win on Sunday it puts us in a very strong position, 4 points ahead of Liverpool with a game in hand. That essentially means we can lose to Everton in our game in hand AND lose another game yet still be 1 point clear of Liverpool, it doesn't guarantee we finish above them, but it makes us strong favourites to do so.
We don't need to win, however. In fact defeat wouldn't be a total disaster, victory in our game in hand would still see us ahead of Liverpool. Personally I see this game as a "must not lose", not mathematically accurate as mentioned above, however in order to keep the pressure off the squad, and to keep it on the Liverpool team, a point would suffice.