Chelsea's trip to Germany was supposed to conclude with progression to the latter stages of the UEFA Champions League as Group A winners, but what transpired saw Werder Bremen toasting a just about deserved 1-0 success.

Poor defending in the 26th minute saw Per Mertesacker expose a makeshift Chelsea back four and in the process give Werder a chance of qualification heading into the final week of group matches.

Chelsea still qualify courtesy of a better head-to-head record against their German counterparts, but on an unsuccessful away day, the English champions failed to ever really hit top gear.

Rivals Barcelona may look on this result with more than a little scepticism but Chelsea were committed if not convincing at the back, energetic if not fluid in attack and there can be few complaints from the Catalan giants.

Chelsea's start at the Weser Stadion was not exactly lethargic but it certainly lacked the poise and bite that normally characterises foreign excursions.

Shorn of the rejuvenate Andrei Shevchenko, who had to settle for a place on the bench, Chelsea crammed their midfield but still looked narrow as Werder worked the flanks well.

With Diego dominating the battle of the number tens, as Joe Cole laboured somewhat on his return, Werder's creative epicentre looked to add craft to Torsten Frings' incessant work-rate at every opportunity.

It was, though, the latter that fired the first warning shot as his drive from the edge of the area required an important block before John Obi Mikel had a glorious chance to mark a rare start with a goal, only to horribly head over after being found free six yards from goal courtesy of John Terry's nod-back.

Carlo Cudicini was brought into action as he gathered Diego's first time snap shot and as the half drew to its midway point, Chelsea were left to rue a dubious piece of officiating.

Frings did not appear to be touched as he went down under a non-existent challenge but referee Lubos Michel ruled a foul. From the resulting setpiece, Mertesacker's header was blocked for a corner. Chelsea would not heed the warning.

Frings swung in from the left and after somehow ghosting in between Michael Ballack and Didier Drogba, the giant Mertesacker powered his header beyond Cudicini.

Mourinho was incensed on the touchline and, on the field, the rough the justice meted out to them seemed to galvanise Chelsea's players, as Joe Cole in particular stepped from the periphery.

A sublime jab with the outside of his right foot presented a chance to Ballack but his flicked finish from close range was meek and Tim Wiese was allowed to save, before, on the stroke of half time, Cole turned his man Pierre Wome cleverly and then ruined his good work with a soft shot straight at Werder's previously underworked goalkeeper.

After the interval and Mourinho needed just over ten minutes to call upon the lexicon of talent available to him on the bench as Arjen Robben and Shevchenko were summoned from the cold.

Chelsea's start to the second 45 minutes mirrored that of the first as a strong running Werder conjured an early chance through Diego's clever run and pass that played in Daniel Jensen, only for Khalid Boulahrouz to spare his side's blushes by hurling himself at the ball in a brave block.

Drogba just failed to get in a shot after a clever one-two with Cole, but of greater concern will be the sight of the Ivorian limping to the touchline, with an injury that could have major repercussions for Sunday's clash with Manchester United.

Shevchenko's first touch could and should perhaps have played in his fellow substitute Robben, but his cross was poor and the chance was lost. As Chelsea began to boss possession, with Werder content to sit and counter, the Ukrainian brought Wiese into action again with a daisy cutter of a free-kick that troubled the unsighted German.

Chelsea showed plenty of endeavour but other than a Michael Essien jackhammer of a strike that went just wide of Wiese's far post, Werder were not forced to suffer too many moments of genuine consternation.

The final minutes saw Chelsea bomb Werder's box with a string of high balls but the Germans stood defiant and at the game's conclusion, it was the home side that yielded what could prove to be a crucial three points in this season's Champions League story.

Teams

Werder Bremen  Wiese, Rodrigues, Fritz, Mertesacker, Wome, Borowski, Frings, Jensen (Hunt 79), Diego, Almeida (Schulz 87), Klose (Klasnic 90)
Subs Not Used Andreasen, Pasanen, Reinke, Vranjes
Booked  Borowski
Goals  Mertesacker 26

Chelsea  Cudicini, Boulahrouz, A. Cole, Terry, Ballack (Wright-Phillips 77), J. Cole, Essien, Makelele, Mikel (Robben 59), Geremi, Drogba (Shevchenko 59)
Subs Not Used  Hilario, Diarra, Ferreira, Morais
Booked  Terry
Goals  

Attendance  40,000

Referee  Kyros Vassaras (Greece)