Bayer Leverkusen moved 10 points clear at the top of the Bundesliga following victory at 10-man Cologne.
After defending champions Bayern Munich were held to a 2-2 draw by Freiburg on Friday, Xabi Alonso's side had a big opportunity to extend their lead.
Their task was aided when Cologne's Jan Thielmann was shown a straight red card for a foul on Granit Xhaka.
Jeremie Frimpong then opened the scoring before Alex Grimaldo's low strike made it 2-0 in the second half.
Leverkusen, who have now gone 34 games without defeat in all competitions this season, are on 64 points with Bayern second on 54.