Bayern Munich could be about to face a difficult summer with a number of players possibly on their way out of the Allianz Arena. The German club have enjoyed unprecedented success in the last couple of years, winning the treble (Bundesliga, DFB-Pokal and Champions League) last season under Jupp Heynckes and have, under Pep Guardiola this time round, already recaptured the league title, as well as the Fifa World Club Cup and Super Cup.However, Bayern could be faced with the task of rebuilding their squad with a number of players believed to be open to the idea of leaving the Bavarians.A source told [football] direct news that midfielder Bastian Schweinsteiger is keen on a new challenge away from Bayern Munich, while others such as Toni Kroos, Xherdan Shaqiri, Mario Gotze and Mario Mandzukic are also heavily linked with possible moves.Kroos has been at the centre of a contractual issue with Bayern, with his current deal at the club coming to an end at the end of next season, which could see the 24-year-old join Manchester United, with various reports claiming the Red Devils hold a strong interest.Shaqiri, since joining from Swiss side Basel in 2012, has failed to hold down a first-team place, despite scoring six goals in just 17 league appearances, and has been linked with a possible move to Liverpool, who can offer Champions League football next season.Another frustrated with a lack of first-team opportunities is Gotze, who only joined Bayern from Borussia Dortmund last summer, which has seen him start only 20 Bundesliga games and completing 90 minutes just nine times.Bayern have already raided Bundesliga rivals Dortmund once again with striker Robert Lewandowski making the move in the summer, which has placed a question mark over Mandzukic, who looks face to lose his place in the side with the Polish international’s arrival and, with 18 goals in the league, it’s doubtful the 27-year-old will be happy as a back-up.