The Packers got down to the mandatory roster limit of 75 players this afternoon by moving 4 injured players to either the physcially unable to peform or injured reserve list, inlcuding starting defensive back Al Harris and safety Atari Bigby.   Harris is attempting to come back from major reconstructive knee surgery after getting inured last November 22 against the San Francisco 49ers.   Bigby was also placed on the PUP list after undergoing ankle surgery shortly after arriving to training camp.  Also placed on the PUP list is rookie running back James Starks.  The 6th round pick from the University of Buffalo pulled a hamstring on the first day of camp and hasn't practiced since.  By going on the physically unable to perform list before the start of the regular season, the players will not be allowed to be reactivated until after the 6th game of the season, against Miami on October 17.  At that point, the Packers will have a three week window to work out the players and do one of three things, put them on the active roster, move them to injured reserve for the rest of the season, or waive them.   With Harris and Bigby out, veteran Tramon Williams moves into the starting cornerback position and 3rd round pick Morgan Burnett will open the season as the starting strong safety.   The Packers also placed running back Quinn Porter on the injured reserve list with an ankle injury, he's now lost for the entire season.