Werder Bremen 1 Chelsea 0: Chelsea qualified for the next phase of the Champions League despite going down to Per Mertesacker's first-half goal against Werder Bremen.

Mertesacker rose unmarked to head home a corner from Torsten Frings to hand Chelsea their first defeat in the competition this season.

Chelsea had plenty of chances to earn the point they needed to win the group, however Bremen goalkeeper Tim Wiese denied both Michael Ballack and substitute Andriy Shevchenko with fine saves.

The defeat, although meaning little in the group, was compounded with the loss of Didier Drogba through injury in the 57th minute.

The loss of Drogba could have serious repercussions for Chelsea, who face Manchester United at Old Trafford in the Premiership on Sunday. The 14-goal striker was helped to the dressing room after appearing to fall awkwardly on his right knee.

In Bulgaria, an early strike by Ludovic Giuly and a second-half goal by Andres Iniesta gave holders Barcelona a 2-0 win at Levski Sofia that kept alive their hopes of qualifying for the knockout stages.

The Spanish giants got the ideal start in the fourth minute when the home defence failed to clear Gianluca Zambrotta's right wing cross and the unmarked Giuly's fearsome shot gave goalkeeper Georgi Petkov no chance.

Barcelona doubled their lead after 65 minutes when Petkov failed to hold on to Deco's long-range shot and Iniesta made no mistake on the rebound.

The Catalans now need to beat Werder Bremen to reach the next phase.