Demichelis out for three weeks
"Demichelis suffered fractures to the eye socket, cheekbone and upper jaw and underwent surgery to repair the damage in the early hours of Thursday morning," Bayern said on their website.
Bayern said the 29-year-old would have to stay in hospital for two to three days and rest for two weeks after a collision with German captain Michael Ballack early in the second half.
Demichelis was overlooked for Argentina's World Cup squad in 2006 but is expected to be included by coach Diego Maradona this time. Argentina won Wednesday's friendly in Munich 1-0.