Bayer Leverkusen took another step towards a first Bundesliga title on Sunday when they won 2-0 at 10-man Cologne to go 10 points clear at the top of the table and stretch their unbeaten run all season to 34 matches.
Cologne's Jan Thielmann was sent off 14 minutes into the regional derby for a reckless challenge against Granit Xhaka, and Jeremie Frimpong opened the scoring in the 37th.
Leverkusen were lucky when Cologne's Sargis Adamjan was denied by the post before Alejandro Grimaldo wrapped up their 30th victory in the unbeaten run in the 73rd.
Xabi Alonso's Leverkusen increased their league lead to 10 points over defending champions Bayern Munich, who were held 2-2 at Freiburg on Friday night. Cologne are third last in the relegation play-off spot.
Leverkusen's first Bundesliga title is becoming more and more possible, and they are also in the German Cup semi-finals, and in the Europa League last 16 where they visit Qarabag on Thursday.
But captain Jonathan Tah warned that "there are still 10 games left and we know what can happen.
"We are happy with the three points and will focus on the next game. We must stay focussed so that things don't get out of control," Tah told streaming portal DAZN.
Looking at the match, he added: "We got a bit nervous when we were one man up. We did better in the second half and played the game confidently to the end."
Jonas Hofmann aimed inches right in the third minute as Leverkusen made their presence felt from the kick-off but Cologne also came close from Dejan Ljubicic's header on the counter seven minutes later.
Cologne were one man down when Jan Thielmann was shown a straight red upon review for stepping onto the heel of Granit Xhaka with no chance of reaching the ball.
Tempers flared a few more times between the Rhine area rivals while it took Leverkusen until the 31st minute to threaten again from Grimaldo's dangerous free-kick.
Florian Wirtz was denied by Cologne goalkeeper Marvin Schwäbe but Leverkusen got the breakthrough in the 37th when Frimpong poked home a low ball from Patrik Schick for his eighth goal of the season.
The hosts tried to hit back and were almost awarded five minutes after the restart when Adamjan hit the far right post.
Chances were sparse from then on before Leverkusen put to the game to bed from Grimaldo's ninth season goal, at the near post and deflected by defender Julian Chabot.
Hoffenheim were hosting Werder Bremen later Sunday to complete matchday 24.
