Barnetta blow for Leverkusen
The Switzerland international requires surgery on torn cartilage in his right knee. He suffered the problem in yesterday's training game against second division Bochum.
"This is of course annoying, but it can't be changed." Barnetta told the club's official website. "After the operation I will do everything I can to make myself available again as quickly as possible."
Bayer lie fourth in the Bundesliga, a point behind second-placed Hannover but 13 adrift of runaway leaders Borussia Dortmund.