Chelsea were held to a 1-1 draw by Schalke in Group G as Jose Mourinho's men were unable to carry their peerless Premier League performances into the Champions League.
The Blues twice beat Schalke 3-0 last season and were strengthened over the summer, while the Germans were severely depleted by injury and reeling from their worst Bundesliga start in more than 40 years.
Cesc Fabregas, one of the summer acquisitions, scored his first Chelsea goal after 11 minutes, despite appearing to foul Max Meyer in the build-up.
Eden Hazard was the provider as part of a sensational individual start, as he set about justifying his imminent new contract and his manager's belief that he can be one of the greats of his generation.
It appeared Chelsea would inflict a heavy loss on their opponents, but Mourinho turned away in disbelief after Fabregas blazed over with the goal gaping and the Blues were warned of Schalke's danger when Julian Draxler came close to an equaliser before the interval.
Didier Drogba, playing in the competition for Chelsea for the first time since his penalty secured the 2012 European Cup, was determined to make a mark but failed to convert from passes by Willian and Hazard.
The misses were punished when Klaas Jan Huntelaar struck on the counter-attack after seemingly fouling Fabregas to win possession in the build-up.
Substitute Loic Remy had a shot cleared off the line before Ralf Fahrmann made a brilliant reflex save to deny Hazard and Chelsea.
Drogba, one of four changes, featured at Stamford Bridge for Galatasaray last term, but now was back in Chelsea blue.
Ramires, included alongside Drogba, Filipe Luis and Willian, shot weakly after fine work from Hazard on the left and then Drogba on the right.
Chelsea took the lead when Meyer delayed on the ball and was tackled by Fabregas in a challenge which appeared late.
Hazard, who had begun the game with some scintillating runs, took the ball on before feeding Fabregas, who slotted the ball through Fahrmann's despairing dive.
The former Arsenal captain celebrated by patting the Chelsea crest on his chest, while Huntelaar was booked for his protestations over the challenge on Meyer.
And if the Dutchman had a point, Chelsea and Hazard, in particular, were not about to show any sympathy.
Hazard had a shot blocked by Kaan Ayhan and continued to terrorise Schalke's rearguard, without captain Benedikt Howedes, who was ruled out with a hip injury on the eve of the contest.
Schalke had fleeting forays forward which amounted to little and Thibaut Courtois, a Champions League finalist last term and first-choice ahead of Petr Cech this season, was little more than a spectator.
Chelsea had numerous opportunities to add to their advantage.
Drogba headed straight at Fahrmann from Luis' cross, Branislav Ivanovic got forward to meet another Luis centre, but was offside.
Ivanovic then latched on to a Ramires lofted pass before pulling the ball back for Fabregas.
It was a straightforward finish for the Spain midfielder, but he lifted the ball high and over.
Courtois was called into action by Kevin-Prince Boateng, turning a 25-yard shot around the post as Chelsea allowed Schalke some space.
A direct Draxler run proved problematic for Chelsea. He ran past Nemanja Matic and Ivanovic and was allowed to shoot, despite the close attentions of Gary Cahill and John Terry, but dragged his effort wide across goal.
Drogba was unable to convert another Willian cross as Chelsea resumed with purpose, with Ivanovic having an effort saved and Hazard curling one over.
Terry had the ball in the net but was booked after being adjudged to have fouled Huntelaar.
With all of Stamford Bridge keen for a Drogba goal, the striker pushed an effort wide after being played through by Hazard.
Chelsea should have been at least 2-0 up, but instead they were brought level when Fabregas was brushed aside by Huntelaar, who fed Draxler.
Draxler ran at the Chelsea defence and returned the ball to Huntelaar, who finished well to equalise as the Chelsea defence backed off.
Chelsea had reason to complain but so, too, had Schalke for Fabregas' strike.
Mourinho threw on Oscar for Ramires and then showed no sentiment as Drogba and Willian were sacrificed for Remy and Diego Costa, the scorer of seven goals in his first four Premier League games.
Remy had an effort headed off the line by Remy Neustadter from a Fabregas free-kick and Hazard volleyed over at the back post as Chelsea fought to reclaim the lead.
Fahrmann then saved well as Hazard stretched to reach a Fabregas cross and Terry went close with a header before Oscar tumbled in the area, with nothing given as Chinedu Obasi won the ball.
Mourinho ran down the touchline to retrieve the ball in stoppage time as Chelsea threw everyone forward, but the Blues now travel to Sporting Lisbon in search of victory after first facing Premier League champions Manchester City on Sunday.