German champions Bayern Munich face a mounting injury crisis with Martin Demichelis being the latest casualty. The Argentinean defender could be sidelined for up to four weeks after sustaining a calf injury in Tuesday's friendly game against Inter Milan. "It could be three or four weeks depending on how the recovery process goes," Bayern coach Jurgen Klinsmann told the club's official website. Demichelis will miss Bayern's first competitive match against Erfurt in the German Cup on Sunday. He also won't be able to take part in Bayern's Bundesliga opener against Mohamed Zidan's Hamburg next Friday. The 27-year-old joins the likes of Franck Ribery, Luca Toni, Tim Borowski, Willy Sagnol and Hans Jorg Butt in Bayern's treatment room.