Moussa Diaby scored one goal and set up the winner for Florian Wirtz as Bayer Leverkusen beat Borussia Dortmund 2-1 on Tuesday to move into second place in the Bundesliga and snap a four-game winless run this year.
The 21-year-old Frenchman was devastating against the Dortmund defence throughout a one-sided first half when he fired the hosts in front, finishing off a quick break in the 14th minute.
He should have added at least one more goal, carving out several good scoring chances.
But Leverkusen rebounded, with Diaby launching another quick move and setting up Wirtz for the winner in the 80th to earn their first win in five league games and move into second place on 32 points. Dortmund are fourth on 29.
"This win was very crucial for us," said Leverkusen's Lars Bender. "After the equaliser we had to overcome some difficult moments and had a bit of luck as well. But we had lots of counter-attacks and luckily scored the winner with one of them."
Dortmund's title hopes suffered a serious blow and the Ruhr valley club have now won just three of their last nine games.
Dortmund are fourth on 29 points and will be 10 behind leaders Bayern Munich if the champions beat Augsburg on Wednesday.
"It was a very disappointing evening for us because we wanted after Saturday's [draw] against Mainz to beat a direct rival," Dortmund captain Marco Reus said.
"The issue of the league title did not play any relevant role before nor after the game."