Bayer Leverkusen moved closer to qualifying for next season's Champions League with a hard-fought 1-0 victory over nearest rivals Schalke 04.
Karim Bellarabi's strike proved enough for the visitors, who now move six points clear of the Royal Blues in the Bundesliga table.
Schalke, who needed a Joel Matip goal to pick up a point at Hertha Berlin last week, almost made the perfect start when Klaas Jan Huntelaar seized on a loose ball in the Bayer box, but he was denied at point-blank range by keeper Bernd Leno.
Bayer found their feet as Bellarabi's deflected effort almost found a way past Timon Wellenreuther.
The German international did find a way through the Schalke rearguard 10 minutes before the break when, after running onto Simon Rolfes's through ball, the forward slotted home from a tight angle.
Roberto Di Matteo decided to reshuffle his pack before the interval with the ineffectual Leroy Sane making way for Kevin-Prince Boateng as the Royal Blues tried to find a way back into the game.
They almost got back on level terms after the restart when Christian Fuchs fired narrowly wide of Leno's goal.
Schalke continued to look for a way back, but both Marco Hoger and Matija Nastasic saw late efforts saved by Leno as Bayer held on for a crucial victory.
