In an NFL.com article, Rapoport was quoted as saying Romo "broke a different bone than last time," when he suffered a fracture in 2014.
For now, we're assuming Romo will miss the first eight games - several reports are saying he'll be out 6-10 weeks. Dak Prescott has played well in the preseason, so for now we're not significantly downgrading the other Cowboys skill players. For the record, HC Jason Garrett didn't give a timetable and labeled Romo as day-to-day, according to an NFL.com story. More as this situation develops.