The 22-year-old suffered a right thigh tear helping Switzerland secure their place at the 2014 FIFA World Cup last Friday, and may not feature again in 2013.
"Obviously I'm not feeling too good," he told fcbayern.de. "It's not what I wanted to hear. I'm disappointed, but will try to get back to fitness as quickly as I can. I've already experienced this kind of tear in my left thigh and actually got fit again relatively quickly. I hope it'll be the same this time."
Bayern have been plagued by injuries already this term, with Mario Götze only recently back in the first-team fold, Javi Martinez set to return to team training this week and Thiago Alcantara currently undergoing rehabilitation following surgery.
Check out what can be expected from fit again summer signing Mario Götze on the official Bundesliga YouTube channel: