The Swabians threw away a 1-0 lead against Bayern Munich on Wednesday night, losing 2-1 deep into stoppage time of a game they could and perhaps should have won.
"The disappointment is huge," said forward Martin Harnik. "In the end, it doesn't matter when you concede the goals.
"We deserved a point and we're going to have to push ourselves to the limit again against Leverkusen."
Defeat instead left them in 12th place, just three points above the relegation zone and 11 adrift of a place in Europe next season.
That position is illusionary, according to their former goalkeeper Bernd Leno, who now keeps goal for Leverkusen.
"Stuttgart have a decent side and don't deserve to be where they are," he said on his club's website.
"They have more quality than they are showing. They're not in good form right now, but we're warned that it's not going to be easy.
"We are both good teams so I think it will be tight."
Both Leverkusen and Stuttgart have added to their squads this week and Carlos Gruezo could make his debut for the visitors having joined from Ecuador.
He has been training with the club since early January and made a good enough impression while on trial to earn a permanent move.
Leverkusen's new signing Andres Guardado is less likely to feature, though, having arrived only on Thursday on loan until the end of the season from Valencia.