Oscar Garcia's side are still in contention for a playoff spot, but they will need to achieve a better result than Reading manage against Burnley on Saturday afternoon.
"We've just got to worry about our end of the bargain," Upson told the club's website. "We must go out there and leave everything on the pitch and what will be will be.
"Obviously we'd love to win the game and know we have done everything we can to force the issue, but it's a little bit out of our hands in terms of the Reading result. But it's a massive game and we've just got to approach it in the right way."
Brighton are currently one point behind Reading, who sit sixth in the table.