Hoffenheim slumped into the bottom two of the Bundesliga after being beaten by a Eintracht Frankfurt side who remain on course for a place in Europe next season.
Frankfurt completed the double over their visitors thanks to goals from Martin Lanig and Stefan Aigner with Kevin Volland bringing Hoffenheim level in between.
The three points keep Frankfurt in fourth place, three points clear of Mainz and three behind third-placed Bayer Leverkusen.
Hoffenheim, meanwhile, fall behind Augsburg on goal difference and, for the first time since being promoted to the top flight in 2008, they are in a position which would see them relegated at the end of the season.
Frankfurt's top goalscorer Alexander Meier wore the captain's armband in the absence of Pirmin Schwegler and he had the first shot of the game in the third minute with Lanig following that five minutes later, hinting at what was to come for Hoffenheim.
The away side came close to netting through Volland's direct free-kick, but Frankfurt held the upper hand and took the lead in the 35th minute.
Lanig's shot took a deflection off Matthieu Delpierre and Andreas Beck was unable to stop it from crossing the line.
Hoffenheim came to life early in the second half with Volland causing the biggest problems.
He set up Firmino for a good chance which Kevin Trapp saved well before he met Beck's cross to bring Hoffenheim level in the 65th minute.
However, Hoffenheim then stopped playing and, just three minutes later, they were behind once again.
Joselu's near-post flick to a corner took his own goalkeeper Tim Wiese out of the equation and gave Aigner a simple tap-in at the far post.
Hoffenheim could not summon the strength to react again and Frankfurt had no problems playing down the clock to earn all three points.