Hertha skipper sidelined with knee injury
Defender Friedrich, a key player in Hertha's bid for a first Bundesliga title since 1931, will have an operation on Wednesday and will be out for between four and six weeks.
"This is extremely bitter because I wanted to help the team in this crucial phase," the Germany defender told the club's website. "I hope to play again during this season and that is my goal."
Hertha are third in the league on 49 points with eight matches left, two points behind leaders VfL Wolfsburg and second-placed Hamburg SV. The league season ends on May 23.