AC Milan meet Barcelona in the Champions League in one of the top European clashes of the group stages.Group A meanwhile promises to be 2011's 'Group of Death'. Roberto Mancini's Manchester City will surely be in for a tough test as they face Bayern Munich, Villarreal and Napoli.Manchester United face Portuguese side Benfica in their Group C, while Real Madrid renew old European rivalries with Ajax.Elsewhere Chelsea meet Valencia, Arsenal play Borussia Dortmund and Porto meet Shakhtar Donetsk, while Inter face French champions Lille.GROUP A Bayern Munich Villarreal Manchester City Napoli GROUP B Inter CSKA Moscow Lille TrabzonsporGROUP C Manchester United Benfica Basel Otelul Galati GROUP D Real Madrid Olympique Lyonnais Ajax Dinamo ZagrebGROUP E Chelsea Valencia Bayer Leverkusen Genk GROUP F Arsenal Olympique Marseille Olympiakos Borussia DortmundGROUP G Porto Shakhtar Donetsk Zenit St Petersburg APOEL Nicosia GROUP H Barcelona AC Milan Bate Borisov Viktoria Plzen