The Bundesliga leaders have been rocked by the groin injury suffered by the 27 - year - old , who has grown into one of Europe 's leading defenders since leaving Manchester City .
Who could be sidelined for up to four months .
The Bundesliga leaders have been rocked by the groin injury suffered by the 27 - year - old , who has grown into one of Europe 's leading defenders since leaving Manchester City , but who could be sidelined for up to four months .