Third-placed Hoffenheim missed a chance to close in on the Bundesliga leaders after having to settle for a 1-1 draw at Cologne on Friday.
Cologne's captain Lukas Podolski fired the hosts into the lead with a left-footed drive as Hoffenheim failed to create any meaningful chances in the first half.
Hoffenheim coach Ralf Rangnick then switched to a risky second-half formation, leaving just two defenders at the back, and the move paid off almost instantly.
Demba Ba stunned Cologne keeper Faryd Mondragon with a shot from the edge of the area to equalise in the 54th minute.
But apart from a Vedad Ibisevic chance a few minutes later, the visitors' attacks quickly fizzled out and Cologne, who had hit the post in the first half, looked more likely winners.
Cologne's Martin Lanig wasted their best chance to clinch all three points 12 minutes from time, firing at well-placed goalkeeper Tom Starke from close range.
Hoffenheim stay third on 11 points from six games, four points behind surprise leaders Mainz 05 who have won all five games and on Saturday visit champions Bayern Munich, who are languishing in eighth place with eight points.
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