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BARCELONA, Spain -- Barcelona got the defense of their Champions League crown off to a dream start when they blew away debutants Levski Sofia 5-0.
Fittingly, the champions became the first team to score in this season's group phase when midfielder Andres Iniesta buried a low shot into the corner from 20 meters out in the seventh minute.
Meanwhile, Germany captain Michael Ballack scored a second-half penalty to earn his new club Chelsea a 2-0 victory over Werder Bremen in Group A.
European champions Barca stamped their authority on the game from the first whistle, Iniesta and a well-taken goal from French winger Ludovic Giuly putting them two goals up by halftime.
Levski, the only Bulgarian side ever to make the group phase, found themselves 3-0 down when Barca captain Carles Puyol added an opportunist strike at the start of the second-half.
Leading striker Samuel Eto'o and World Player of the Year Ronaldinho then completed Barcelona's biggest win in the Champions League with stunning individual efforts.
It was the sixth time in a row that Barcelona have won their opening Champions League game, a victory that extended their unbeaten run to 14 matches.
Barca took to the pitch wearing their new shirts advertising their collaboration with the United Nations children's agency UNICEF and celebrated the occasion by becoming the first team to score on the opening day of this year's competition.
Midfielder Iniesta buried a 20-meter shot low into the corner after Eto'o had unselfishly laid the ball into his path following some dazzling work by Ronaldinho on the left.
Levski were certainly not in awe of Barca and took the game to the Catalans whenever they could wrest the ball from their control.
Defender Stanislav Angelov had a good chance to level the scores in the 20th minute after a slick counter-attack, but drove his shot straight at Barca keeper Victor Valdes.
A heavy downpour dampened spirits for the next quarter of an hour, but Barca stepped up a gear just before the break and extended their lead after the ever alert Iniesta slipped the ball to Eto'o after taking a quick free kick on the halfway line.
Eto'o unleashed Giuly with a deft first time pass and the French winger whisked his way past two defenders before clipping the ball over the diving Petkov to make it 2-0.
Club captain Puyol added a third four minutes into the second half with only his fourth goal for the first team when he stabbed home after Petkov was unable to hold Ronaldinho's free-kick.
Levski pushed forward when they could, but went unrewarded and they could do nothing to stop Eto'o making it 4-0 when he bamboozled his way past three defenders as he steamed towards the area then side-footed the ball home past Petkov.
Barca's fifth was every bit as good, Ronaldinho unleashing a couple of trademark stepovers on the left side of the area before curling a perfectly struck shot out of reach of Petkov and inside the far corner in the final move of the match.
At Stamford Bridge, Ballack, stepping up instead of Chelsea's usual penalty taker Frank Lampard, who has had little success from the spot recently, added to midfield dynamo Michael Essien's 24th minute strike from close range.
Bremen, renowned for their attacking flair, kept the pressure on the English champions and World Cup golden boot winner Miroslav Klose was particularly dangerous, hitting the bar with a header in the second half.
Lampard also hit the post in a fast and furious end-to-end game that put Chelsea level on points with rBarcelona at the top of the group.
For an attacking side Bremen held a tight back line for the first 20 minutes, keeping out strikers Andriy Shevchenko and Didier Drogba.
It was an unfortunate tumble on Stamford Bridge's slick surface that allowed the home side through.
Lampard, driving through the middle, was dispossessed by defender Petri Pasanen but the Finn slipped in the area, poked the ball through to Essien and the Ghana midfielder slammed it home for his first Chelsea goal in European competition.
That prompted Bremen to resume their natural game.
They opened up on the wings and tested Chelsea's defence with a rampaging run by Klose, whose shot ricocheted away for a corner off Khalid Boulahrouz's head. Minutes later defender Pierre Wome piled through the midfield and went close.
Ivan Klasnic and Brazilian Diego also had chances in the second half and it was as the Germans looked their most dangerous that Drogba earned the penalty on the counter-attack.
He was forced over in the area by Clemens Fritz and Greek referee Kyros Vassaras pointed immediately to the spot.
Ballack, who left Bayern Munich for Chelsea in the close season, had suffered taunts from the travelling fans all through the game but made no mistake with his 68th-minute spot kick.
Only on Monday, Chelsea coach Jose Mourinho confirmed Lampard as his penalty taker despite the England midfielder missing three out of his last four for club and country. He had left open the possibility, however, that Lampard might delegate the duty on the night if he wished.
Barcelona players celebrate another goal as Levski were outplayed in the Nou Camp.