Cologne gave themselves a great chance of qualifying for the next round of the Europa League, with a 1-0 win over Arsenal on Thursday night.
Sehrou Guirassy proved to be the match winner, slotting home a controversial penalty in the 62nd minute of the game.
The goal came against the run of play and the home side were content to sit back and defend it, as the Gunners attacked relentlessly in the hope of getting an equalizer.
Arsenal remain top of Group H with one game remaining.
Arsene Wenger’s men have 10 points from their first five group fixtures, while Cologne and Red Star Belgrade have six points each. BATE Borisov remain bottom with five.