Chelsea's hopes of qualifying for the last 16 of the Champions League are in the balance after a late winner gave Bayer Leverkusen a 2-1 win in Germany.
The Blues knew victory would see them through and they looked in good shape after Didier Drogba's neat finish.
But substitute Eren Derdiyok headed Leverkusen level with 17 minutes to go.
In the final minute Manuel Friedrich headed in to leave the Blues needing a goalless draw or win against Valencia in two weeks' time to progress.
It was a cruel blow for Chelsea, who had done enough to claim at least a draw from this match, but are now left to face a nerve-jangling final Group E matchday encounter with the Spanish side, who put seven goals past Genk on Wednesday.
Chelsea came into the game having lost three of their previous four league matches, leading to suggestions that manager Andre Villas-Boas was under pressure, only months after Roman Abramovich paid £13.3m to acquire his services from Porto.
But while not truly impressive, and despite the result, this was a much improved performance from those three defeats.
Gone was the ill-discipline that marred the loss at QPR, there was none of the suicidal defending that cost them against Arsenal and they were more composed and fluent than at any point during the defeat by Liverpool.
In Daniel Sturridge they had the best player on the pitch, particularly after the match had settled down midway through the first half.
The young England striker was central to everything positive about the Blues in the final third, firstly narrowly over-hitting a through-ball for Juan Mata before getting it spot on second time round to feed in Drogba, who subsequently missed from a tight angle after rounding the keeper.
DID YOU KNOW?
The last 10 times that a Chelsea Champions League away match was scoreless at half-time, the Blues have gone on to win just once. That was at FC Porto on 25 Nov 2009 (0-1)
Leverkusen were left to rely on their former Chelsea midfielder Michael Ballack in his 100th European game and he nearly delivered before the break with a header from a corner that hit the bar.
But Sturridge was not to be out-shone and early in the second half he provided an inch perfect pass to Drogba, who held off Friedrich before slotting a neat finish into the bottom corner on the turn.
The Blues almost extended their lead a minute later but Frank Lampard headed straight at keeper Bernd Leno from close range following Drogba's nod-on.
That proved something of a turning point as Leverkusen, off the back of the reprieve, seized control of the match.
Stefan Kiessling served warning to the visitors with a header straight at Cech from a Gonzalo Castro cross before substitute Derdiyok was found in plenty of space at the back post by Sidney Sam to head home an equaliser.
Chelsea had a penalty appeal waved away when Drogba fell under a challenge from Friedrich and the Ivory Coast striker volleyed wide soon after as the game appeared destined to end in a draw.
However, with injury time signalled, Friedrich won the game for the home side, rising to plant a header in off the bar from Castro's corner.
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