Bayer Leverkusen came from behind to beat Bayern Munich 3-1 and land another damaging blow against the champions' Bundesliga title defence.
Ex-Borussia Dortmund head coach Peter Bosz did his former club a huge favour despite Leon Goretzka giving Bayern a 41st-minute lead.
Leon Bailey launched a fabulous free-kick into the top-left corner before Kevin Volland and substitute Lucas Alario sealed victory for a vibrant Leverkusen, who move up to seventh in the table.
Instead of being punished for their 1-1 draw at Eintracht Frankfurt, Dortmund's lead over Bayern at the summit edges up to seven points.
Mats Hummels survived an early penalty shout for handball when he blocked Volland's shot at close quarters.
Kingsley Coman made the most of the hosts' high line to charge in on goal. Lukas Hradecky saved but Thomas Muller sent the ball back into the box from the right for Goretzka to head home.
Lewandowski thought he had made it 2-0 in first-half stoppage time, but a VAR review confirmed he was fractionally offside before stylishly converting Coman's pass.
Bosz's men made the most of that let-off by restarting on the front foot and Bailey's wonderful strike brought them level after Coman tripped Volland.
Bayern goalkeeper Sven Ulreich scampered towards the same corner to claw Julian Brandt's 60th-minute volley behind.
James Rodriguez had a close-range header blocked but a late Bayern onslaught never truly materialised before Alario dispatched Brandt's low cross in the 87th minute.
Attacking verve, a relentless tempo and a perilously high defensive line – the year Bosz spent contemplating his Dortmund exit has not shaken his principles on the evidence of this thrilling Leverkusen display. Bayern must now make up seven points over the remaining 14 games, with the Bundesliga title slipping a little more from their once-firm gasp.
Bayern's defence regularly appeared ill at ease with Leverkusen's livewire forward line and centre-back Niklas Sule erred badly on the winning goal. His decision to leave Volland and launch a desperate lunge on Bellarabi in full flight was flawed in both conception and execution. The Germany international will also not look back on Alario's goal with any fondness.
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