Stuttgart sack coach Keller
Two days after their 2-1 defeat at Hanover 96, Stuttgart unveiled the 44-year-old Labbadia, who had previously coached Hamburg SV and Bayer Leverkusen, as their new coach, the third this season.
"This is an interesting task and one I have great respect for," Labbadia told reporters in a hastily arranged presentation.
"I am aware of the difficulty of the situation where we are not five minutes before 12 but a step beyond that. But I am convinced we can do it and we will. I hope we can allow the sun to shine again in half a year."
Keller had succeeded Swiss Christian Gross in mid-October but was unable to lift the club off the bottom spots in the Bundesliga.
While Stuttgart are cruising in the Europa League, topping their group with 12 points and four wins from five games, they are stuck in 17th spot with 12 points from 16 games in the 18-team domestic league.
Under Keller they won just two of their nine league games.
The last time the 2007 Bundesliga champions were relegated was in 1975 after they conceded 79 goals in 34 games.