Needing to win to maintain their interest in the competition, Anderlecht went ahead through Christian Wilhelmsson near the half-hour, but Klasnic struck either side of the interval to give the German champions a hard-fought and valuable success.
 In front of a sell-out crowd, Anderlecht made a bright start on a pitch made greasy by a heavy thunderstorm which broke over Brussels before the kick-off. Visiting goalkeeper Andreas Reinke fisted away a dangerous Wilhelmsson cross, and Bremen defender Valérian Ismaël was booked for holding back Mbo Mpenza as the pacy striker looked to break clear early on.
 Bremen soon settled and went close to breaking the deadlock after 12 minutes, when front-runner Miroslav Klose headed narrowly wide from Johan Micoud's cross after the Frenchman's silky skills had created space on the right flank.
 The visitors began dominating, with Micoud a constant threat in midfield, and Swiss international Ludovic Magnin shot past the post when well-placed in the area. But Anderlecht came back after a subdued spell, Pär Zetterberg volleying into Reinke's arms from 20 metres. Paul Stalteri became Bremen's second booking for bringing down Fabrice Ehret before Anderlecht broke the deadlock on 26 minutes. Vincent Kompany surged down the right and crossed low for Wilhelmsson to prod the ball in at the near post.
 A hectic, fiercely-contested first half continued with Wilhelmsson cautioned for fouling Magnin before Bremen hauled themselves level in the 35th minute. Anderlecht goalkeeper Daniel Zitka dived at the onrushing Klose's feet from Micoud's through pass, but the ball ran loose for Klasnic to fire into the net.
 The score reflected the game's tight nature, with both teams giving no quarter. Zitka saved Magnin's low shot at one end, and Reinke dived to push away Wilhelmsson's teasing, bouncing cross as an entertaining, even first half reached its conclusion.
 The rain had thankfully stopped as the second half got under way and Bremen forced the pace on the restart with a series of corners, none of which brought reward, before Zitka beat out a fierce Klose drive. But Anderlecht responded quickly as the game continued to ebb and flow, Ivory Coast striker Aruna Dindane glancing a header wide from Wilhelmsson's corner.
 Bremen left-back Christian Schulz was shown the yellow card for fouling the lively Wilhelmsson after 56 minutes, but the determined German side grabbed a well-worked second goal near to the hour. Klose and Micoud combined skilfully in the area, and the unmarked Klasnic made no mistake from close range.
 Anderlecht were rocked back on their heels by the goal, and Klose should have done better than shoot wide when he broke clear on the right. The home side's coach, Hugo Broos, tried to turn the tide, replacing Ehret and Besnik Hasi with Goran Lovré and Oleg Iatchtouk, but Bremen were looking comfortable as the game entered its closing stages.
 Anderlecht threw caution to the wind as the minutes ticked by, Reinke saving acrobatically from Walter Bassegio. But their desperate efforts came to nothing – and Klasnic's two goals consigned them to their third straight defeat.