The Holland international sustained the injury just before half-time in the 2-1 pre-season friendly defeat to United in Washington and was replaced by Isaac Cuenca.

According to the Barca website, the 25-year-old Afellay is likely to be out for between "four to five weeks", meaning he would miss next month's Spanish Super Cup against Real Madrid, the UEFA Super Cup against Porto and the start of the new Primera Division season.