RB Leipzig did not get off to the ideal start in the Bundesliga after suffering a 1-0 loss to Mainz on Sunday afternoon.
New signing Andre Silva started up front Leipzig while Marcel Sabitzer only started on the bench as he continues to be linked with a departure.
While all eyes were on new Leipzig coach Jesse Marsch, it was the home side who walked away with three points on the day thanks to Moussa Niakhate's 13th minute strike.
Leipzig will look to bounce back next week against Stuttgart, who managed to thrash Greuther Furth 5-1 on Saturday.
FC Cologne opened their Bundesliga season with a 3-1 victory over Hertha Berlin at the RheinEnergieStadion.
The visitors got off to the perfect start when new signing Stefan Jovetic marked league debut with a goal after just five minutes.
The home side had to wait until the 41st minute to get back on level terms, with Anthony Modeste finding the back of the net.
The turnaround was complete on 52 minutes thanks to Florian Kainz, who managed to complete his brace three minutes later and extended Cologne's lead in the process.
