Tough Champions League draw for Arsenal increases pressure on Arsene Wenger to find recruits Arsène Wenger's side, who have made just two free signings this summer, were last night drawn in Group F with Marseilles, Borussia Dortmund and Napoli. Given injuries - Lukas Podolski is out for 10 weeks - and departures, there is even more of a need to spend in the final days of the transfer window - even after yesterday's arrival of Mathieu Flamini on a free transfer - if they want to qualify for the last 16. Drawing Dortmund and Napoli from pots three and four respectively made it the hardest draw Arsenal could have received, despite being seeded in pot one. Dortmund were last year's beaten finalists, losing 2-1 to Bayern Munich at Wembley. They won the Bundesliga in both 2010-11 and 2011-12 and have proved their ability to play attacking, energetic football, despite the departures of key players. This summer they lost Mario Götze to Bayern Munich for €37m (£31m) but have reinvested the money, signing Henrikh Mkhitaryan from Shakhtar Donetsk - beating off interest from Liverpool - as well as Pierre-Emerick Aubameyang from Saint-Etienne and Sokratis Papastathopoulos from Werder Bremen. Jürgen Klopp's team have started the season well, beating Bayern 4-2 in the German Super Cup last month. Napoli are another side who have sold big and reinvested this summer, spending the £53m they received from Paris Saint-German for Edinson Cavani on Gonzalo Higuain, Pepe Reina, Jose Maria Callejon, Raul Albiol, Dries Mertens and more, and are now managed by the former Chelsea interim coach Rafael Benitez. Marseilles are the least-threatening side in the group but still finished second in Ligue 1 last season and have the talented Ghanaian international winger Andre Ayew and France midfielder Mathieu Valbuena. Even Manchester City, seeded in pot three, have an easier group than Arsenal, with Bayern Munich, CSKA Moscow and Viktoria Plzen, raising their hopes that they might progress out of the group stage after two unsuccessful attempts. Bayern, the reigning European champions who are competing in tonight's Super Cup, are obviously City's hardest opponent. City will be returning to the ground where, in September 2011, they lost 2-0 and there was the infamous touchline dispute between Roberto Mancini and Carlos Tevez. Bayern have arguably improved since then, winning the Bundesliga and Champions League last season and this summer bringing in coach Pep Guardiola and young midfielders Götze and Thiago Alcantara. Unlike in previous years, the other two teams might prove less difficult. But CKSA Moscow, the Russian champions, have impressive firepower in Seydou Doumbia, Alan Dzagoev and Ahmed Musa, as well as Russia's international goalkeeper Igor Akinfeev. The fourth team are lower-profile. Viktoria Plzen won their second-ever Czech title last season, and play in front of just 11,700 fans in the Doosan Arena. In their first Champions League experience, in 2011-12, they finished third behind Barcelona and Milan. Manchester United and Chelsea were rewarded with easier groups than Arsenal or City. This is David Moyes" first year in the Champions League and while United will face three good teams, it is not a comparable challenge. United will have to make the long journey to Shakhtar Donetsk in Ukraine, where they will face a team who are always dangerous even after this summer's sales - Fernandinho, Razvan Rat and Mkhitaryan have all left. Douglas Costa - who United failed to sign from Gremio in 2010 - is there, along with new arrival Bernard, the 20-year-old Brazilian who won the Copa Libertadores with Atletico Mineiro this summer. Real Sociedad have had their own departures - coach Philippe Montanier and midfielder Asier Illarramendi - but they beat Lyons so well in the play-off that they should be considered difficult, technical opponents. Bayer Leverkusen finished third in the Bundesliga last season and will not be a popular opponents for United after the memories of 2002. That year they beat United in the Champions League semi-final, fighting back to draw 2-2 at Old Trafford in the first leg before holding United to a 1-1 draw in the BayArena. They went on to lose the final 2-1 to Real Madrid, while United did not get to another European Cup final until 2008. Chelsea, who won the Europa League last season after being eliminated from the Champions League at the group stage, have a comfortable-looking draw in Group E, the easiest an English team was given - including two teams they beat in last year's Europa League run. Jose Mourinho's side will play FC Basel, the Swiss champions whom they beat 5-2 in the semi-final last season. Basel, who have attacking talent in Mohamed Salah, Valentin Stocker and Marco Streller, had knocked out Tottenham in the quarter-finals. Chelsea will also face Steaua Bucharest, whom they beat 3-2 on aggregate in the round of 16. The hardest opponents will be the Bundesliga side Schalke 04, who reached the semi-finals of the Champions League in 2011 when they were well beaten 6-1 by Manchester United. In Julian Draxler they have one of the most exciting teenagers in Europe. Celtic have been rewarded for their 3-2 aggregate win over Shakhter Karagandy with another difficult group, at least as hard as Arsenal's, as Group H includes Barcelona, Milan and Ajax. Last year Neil Lennon's side famously beat Barcelona at home on their way to qualifying from their group and meeting Juventus in the last 16. This group, though, is even harder. Milan just overcame a good PSV Eindhoven side in the play-offs while Frank de Boer's Ajax have won the last three Dutch titles. Champions League groups... Group A: Manchester United, Shakhtar Donetsk, Bayer Leverkusen, Real Sociedad Group B: Real Madrid, Juventus, Galatasaray, Copenhagen Group C: Benfica, PSG, Olympiakos, Anderlecht Group D: Bayern Munich, CSKA Moscow, Manchester City, Viktoria Plzen Group E: Chelsea, Schalke, FC Basel, Steaua Bucharest Group F: Arsenal, Marseille, Borussia Dortmund, Napoli Group G: Porto, Atletico Madrid, Zenit, Austria Wien Group H: Barcelona, Milan, Ajax, Celtic