Borussia Dortmund slipped back to the bottom of the Bundesliga despite picking up a point in their goalless draw at Bayer Leverkusen.
Cologne dumped Hamburg right into the thick of a relegation battle with a 2-0 win at the Volksparkstadion.
Wolfsburg reduced Bayern Munich's deficit at the top of the Bundesliga to 11 points after a 2-1 win over Cologne.
Bayern Munich continued their unbeaten start to the Bundesliga season with a 2-0 win over Freiburg on Tuesday night.
Mainz's winless run in the Bundesliga stretched to eight games as they came away from Cologne with just a point.
Schalke suffered their first home defeat under Roberto Di Matteo as Cologne claimed a precious 2-1 win.
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