VfL Wolfsburg beat Bayer Leverkusen 1-0 on Saturday with a winner from Ridle Baku, to join them on 32 points and climb into the top four of the Bundesliga.
The result was a setback for Leverkusen, who had been hoping to close the gap with second-placed RB Leipzig.
Leipzig were unexpectedly beaten by strugglers Mainz but Leverkusen's own defeat left coach Peter Bosz ruing a string of missed chances.
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"At then end of the day Wolfsburg deserved to win," Bosz said. "We started really well and had huge chances. You need to make the most of those against a team like Wolfsburg.
"Towards the end we lacked freshness and power."
Leverkusen went into the game with their best first half a season in seven years and having beaten Borussia Dortmund last week.
They came close to scoring in the opening minutes but Nadiem Amiri's effort was cleared on the line and Lucas Alario's header bounced off the post.
The Wolves grabbed the lead when Baku headed in a smooth cross from Renato Steffen at the far post.

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Wolfsburg defended deep but the hosts struggled to break past their opponents' defence.
It was a similar picture after the break with Leverkusen enjoying almost complete possession but having almost no chance to score.
"We started badly but then we gradually improved," said Wolfsburg coach Oliver Glasner. "In the second half Leverkusen were pressing but we did not allow them a single chance. Congratulations to the lads for their tactical discipline."
Wolfsburg, who have lost just twice in the league so far, are level with third-placed Leverkusen on 32 points. Leaders Bayern Munich, on 39, take on Schalke 04 on Sunday.
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