Arsene Wenger will be looking for Arsenal to deliver a performance against Borussia Dortmund in the Champions League on Tuesday which can lift the gloom surrounding the club. Aside from Wenger's side taking on the German champions the pick of the opening round of group matches is holders Barcelona hosting Italian giants AC Milan while former German captain Michael Ballack is in the mix to play for Bayer Leverkusen against one of his former clubs Chelsea. While Arsenal at least go into the Dortmund clash with a victory, a 1-0 win over Premier League newboys Swansea is hardly a resounding sign that things are on the mend, but Wenger will take anything at the moment as a boost. "When you don't win you have a deep problem, that's for sure, the longer it lasts, the deeper the problem becomes. "And as soon as you win things are different," said Wenger, who has admitted that he is well prepared for hell after events over the past few months. Wenger can take heart, though, that his side are facing a Dortmund outfit also lacking in confidence after making a shaky start to their title defence, and went down to a surprise 2-1 home defeat on Saturday to Hertha Berlin. However, club captain Roman Weidenfeller has urged his team-mates to keep cool in light of the defeat and with the chance of rebounding against Arsenal. "We need to remain calm and continue to build on our strengths: determined and compact defending after we have attacked. We need to fix the mistakes we are making," he said. Barcelona gave Milan some cause for optimism at the weekend as they uncharacteristically let slip a 2-0 lead to be held 2-2 away at Real Sociedad and lost star Chilean wing Alexis Sanchez for probably two months after he tore a hamstring. Nevertheless Barcelona should be boosted by the return of talismanic central defender Carles Puyol who was fit enough to return to the bench on Saturday. Their in-form former Arsenal captain Cesc Fabregas - who scored his fifth goal for them since joining from the Gunners last month - is confident they will come back from that slightly disappointing performance. "We know how to win, how to lose, how to play and how to get back and this is what is important," Fabregas told Sport.es. Milan warmed up for the mouthwatering clash with an entertaining 2-2 draw at home to Lazio on Friday which saw them do the reverse to Barcelona in coming from 2-0 down to grab a point. Brazilian striker Alexandre Pato, who is engaged to Silvio Berlusconi's daughter, is likely to return after being rested following the Copa America. Milan's Ghanaian midfielder Kevin-Prince Boateng believes, though, that Milan have nothing to fear from their opponents. "Barcelona unbeatable? If I believed that then I wouldn't be playing football. Every team can be beaten," the midfielder told La Gazzetta dello Sport. "We have to be compact against Barcelona because we are away from home and so we have to defend well. "Up front we have excellent forwards, and so we will score against them sooner or later. "If we block Xavi and Andres Iniesta then it will be difficult for them to score. "I think the game will end in a 1-1 draw." Chelsea entertain Bayer Leverkusen after maintaining their unbeaten start to the season and worryingly for their German opponents manager Andre Villas-Boas believes that their performance over Sunderland was the one they had been waiting for. "It went very well for us in terms of what we want to achieve," said Villas-Boas. "Not that we haven't tried to do it before but it just didn't happen in the other three games. "Fortunately, we were able to do the passing game that relates more to how we train and I have to say we're very happy." Whether Ballack lines-up against his former team-mates lies with Bayer coach Robin Dutt but after an impressive performance in the 4-1 win over Augsburg there is every chance the 34-year-old veteran will be on the pitch.