Bayern Munich have confirmed that Javi Martinez is facing a lengthy spell on the sidelines after tearing his anterior cruciate ligament (ACL) in the club's 2-0 defeat to Borussia Dortmund on Wednesday. Martinez, 25, will not play for Bayern again in 2014 and could face up to seven months out of action. The Spain international suffered the injury when he tried to reach a ball with a scissor kick in the 29th minute of the German Super Cup. While he reached the ball, he also hit Dortmund left back Marcel Schmelzer's elbow, and landed in pain. He was stretchered off the pitch minutes later. "The concerns have proven true. Javi Martinez has suffered an ACL tear in his left knee during the Supercup in Dortmund on Wednesday," a statement on Bayern's official website read. Martinez was quoted as saying: "Of course, I am sad right now. But you need not worry, I will come back even stronger." Bayern announced that Martinez will fly out to the United States in the next couple of days to undergo surgery in Vail, Colorado. He will begin his rehab upon his return to Munich. "I've damaged my knee and right now, I'm on the team bus. I've spoken to the doctor and he's told me that there is a 99 percent chance that I have torn my cruciate and external ligaments," the player said on a video published on his Facebook page on Wednesday. The Martinez injury limits Pep Guardiola's defensive options. In Dante and Jerome Boateng he only has two fully fit centre-backs in his squad. The latter is suspended for the Bundesliga curtain-raiser against Wolfsburg this weekend after a red card against Hamburg in the dying minutes of a game towards the end of last season. Germany international Holger Badstuber has only just returned from a 19-month long spell on the sidelines following an ACL tear in December 2012, and Austria international David Alaba prefers to play on the flanks. In preseason, Guardiola had tested a 3-4-3 formation, with Martinez playing in the sweeper role — an experiment that had already won FC Bayern the DFB-Pokal against Borussia Dortmund in May 2014.