Keller's side appear certain to qualify for the UEFA Champions League, sitting third in the Bundesliga and seven points clear of Bayer Leverkusen.
Huub Stevens' Stuttgart are just a point ahead of the relegation play-off place ahead of the clash at the Mercedes-Benz Arena.
Keller is wary of the threat Stuttgart will pose to his team, and said Stevens' men were better than to be fighting for their place in the top flight.
"I don't think that Stuttgart are near the relegation zone because they don't have enough quality," he told a news conference on Friday.
"They have really had a lot of misfortune, when you look at all the matches which they've lost within the last minutes. In most of these matches they've been the better team. So more faults appeared, and a lack in concentration.
"It's everything but an easy challenge for us, especially as their head coach Huub Stevens will motivate them a lot.
"They really need these three points and do have great quality in their squad."
The outing is also a special one for the Stuttgart-born Keller.
The 43-year-old had two stints at the club as a player, and was an assistant and coach at Stuttgart before moving to Schalke.
"For me personally it's a very special game against Stuttgart," Keller said.
"This is the club where I grew up, where I played as a young player and took my first steps as a professional, where I earned my first credits as a coach.
"I only grew up four, five kilometres away from there. Of course it is a special game for me. Nevertheless I go there to win because we want to reach our goals. I want to win in Stuttgart."
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