The Packers on Tuesday placed Cobb on the injured reserve/designated for return list. The team's leading receiver left Sunday's 19-17 win against the Baltimore Ravens with a leg injury that ESPN senior NFL analyst Chris Mortensen confirmed was a fractured fibula.
The designated-for-return rule, which went into effect last season, allows teams to place one player per season on injured reserve and then bring him back later in the season. Cobb must stay on that list for eight weeks before he can return. He can begin practicing after six weeks.
That would allow Cobb to return for the Packers' final three regular-season games, beginning with the Dec. 15 game at Dallas.
The Packers used the IR/designated for return option last season on running back Cedric Benson, who sustained a Lisfranc foot injury in Week 5, but Benson never returned.
The Packers on Tuesday also placed backup offensive lineman Greg Van Roten on injured reserve. He sustained a foot injury in practice last month.
The Packers filled the two open roster spots by promoting receiver Myles White and tight end Jake Stoneburner from the practice squad. Both undrafted rookies were in training camp with the Packers.
In addition to being without Cobb, the Packers are not sure whether receiver James Jones will be available for Sunday's game against the Cleveland Browns. Jones sustained a knee sprain against the Ravens. Coach Mike McCarthy said Monday that Jones has a chance to play this week.