The goalkeeper, on loan for Liverpool, says that Rafa Benitez's men are out for all three points in their crucial Champions League group-stage clash against the Germans
The Serie A representatives will book their ticket for the knockout stages with a draw against last season's runners-up but Reina the goalkeeper warns that the Partenopei will be gunning for the full three points as they aim to return to winning ways in the wake of two domestic defeats.
"We know a draw would see us through but we should not play for one. That could be very dangerous," Reina told reporters.
"We have to try to play our own game and not focus too much on what Dortmund are going to do.
"We go into [Tuesday]'s game with even more determination to win after the two recent defeats. While you are maybe allowed to lose at Juventus, the home defeat against Parma was more of a shock to us."
Napoli currently sit joint-first in Group F with Arsenal with nine points from four games, holding a three-point lead over third-placed Dortmund.