Green Bay will be without center-guard JC Tretter for the first eight weeks of the regular season after the Packers placed him on injured reserve-designated for return Wednesday.

To take Tretter's place on the roster, the Packers signed center Garth Gerhart from the practice squad. They also signed guard Josh Allen to the practice squad.

With Tretter sidelined, rookie fifth-round draft pick Corey Linsley from Ohio State will take over at center for the opener against the Seattle Seahawks on Thursday night.

Tretter suffered a left knee injury on Aug. 22 in a preseason game against the Oakland Raiders. He will be out until after least the Nov. 9 game against the Chicago Bears.

Gerhart, the brother of Jacksonville Jaguars running back Toby Gerhart, was on Green Bay's practice squad at the end of the 2012 season and again for the final 12 weeks and playoffs in 2013. He also has been on practice squads with the Cleveland Browns and the Carolina Panthers.

Allen was cut by the Tampa Bay Buccaneers on Sunday.