Simon Terodde scored a brilliant opening goal in the 14th minute for Cologne — turning smartly and firing in after Jonas Hector had played the ball forward to Schindler with his heel — but Mainz struck back with three goals to climb out of the relegation zone.
Jean-Paul Boetius equalized seven minutes later, then set up Robin Quaison to let fly for the home side's second in the 57th. Levin Öztunali capitalized on a mistake from goalkeeper Timo Horn to seal the win in the 82nd. Horn had the near post covered but the midfielder's shot still got through.
Left to rue a fine performance from Mainz goalkeeper Robin Zentner, Cologne is in the relegation zone ahead of the rest of the ninth round.
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