-LRB- CNN -RRB- -- Fernando Torres rediscovered his scoring touch with a double at Stamford Bridge as Chelsea romped to a 5-0 win over Genk in their Champions League Group E match Wednesday . The Spanish international striker had not scored in European club football for over two years , but looked dangerous throughout and might easily have had a hat-trick . The Belgian visitors were up against it from the start and after Torres hit the post , Raul Mereiles scored with a thumping shot from outside the penalty area . Torres was soon on the score sheet with a neat side foot effort and added his second with a well-placed header from a Mereiles cross . Branislav Ivanovic headed home from a Florent Malouda free kick for the fourth just before halftime . Torres , who was rested at the weekend , looked sharp as he went in search of his third and he was denied by Genk keeper Laszlo Koteles only for Salomon Kalou to grab the fifth from the rebound . Chelsea lead Bayer Leverkusen by a point after the German side beat Valencia 2-1 in the other Group E match . Former Chelsea midfielder Michael Ballack was the inspiration for Leverkusen , who fell behind to a goal from Brazil striker Jonas . But they hit back through goals by midfielders Andre Schuerrle and Sidney Sam after the break , with ex-Germany captain Ballack setting up the winner with a superb defense-splitting pass . Meanwhile in Group F , Arsenal made sure it was a good night for English Premier League sides with a last-gasp victory over Marseille in the Stade Velodrome . The game was headed for a 0-0 draw when substitute Aaron Ramsey cropped up for the precious winner as Arsenal go top of the group by a point from their French opponents . Olympiakos of Greece beat German champions Borussia Dortmund 3-1 in the other match in the group to keep alive their hopes of qualification for the knockout stages . Jose Holebas , a German player of Greek descent , headed the opener for the home side after just eight minutes . Dortmund deservedly leveled through Polish striker Robert Lewandowski midway through the first half , but five minutes before the break Rafik Djebbour restored the Olympiakos lead . With the visitors pressing , Olympiakos broke upfield to win a free kick and defender Francois Modesto headed home from Ariel Ibagaza 's delivery to seal the victory .