The Green Bay Packers are trying to do without.

It's a familiar predicament for them. But injuries are piling up at the offensive skill positions and in many cases to players who need training camp to assure themselves of a roster spot. It has spread from rookies to veterans and sidelined starters and backups alike.

The latest big news was that two of the Packers' top three wide receivers were somewhere other than where they were supposed to be.

Jordy Nelson was recovering from a surgical procedure on his knee and has been declared out for the rest of training camp. Randall Cobb was on the sideline with a bag of ice on his arm after leaving practice with a biceps injury the seriousness of which hasn't been revealed.

Nelson's surgery was to clear up a lingering problem and done with the intention of having him ready for the start of the regular season. He probably could not have waited any longer for the fix without having to sacrifice at least the season opener.

"Fortunately with Jordy his particular thing that we had to go and fix is something that we have some experience with with some other guys here" general manager Ted Thompson said. "So we think we can predict about the way it'll go but you never know."

Neither Thompson nor coach Mike McCarthy was specific on what was ailing Nelson. His agent Vann McElroy did not return a phone message seeking comment. NFL.com reported it was a minor issue Nelson has been dealing with since his days at Kansas State.

Nelson ruptured a bursa sac in a knee in Super Bowl XLV and missed all but a handful of plays against Minnesota on Dec. 2 because of a knee injury but has not suffered anything that kept him out for an extended period of time. The Packers are hoping this surgery ends any trouble he has been having with it.

"Our hope is for Jordy to be ready for the season opener at San Francisco" McCarthy said.

On the same day Nelson's surgery was announced Cobb dropped out of practice during a team drill. Cobb had an ice bag near his shoulder area but stuck around and spent time during and after practice running sprints.

McCarthy offered no more information on Cobb but there's no question he was keeping his fingers crossed it was a minor injury.

Missing two of their top three receivers would be more of a problem if this were Sept. 6 instead of Aug. 6 but it is a recurring theme for the Packers. They have already lost free-agent receiver Sederrik Cunningham to a season-ending wrist injury and are waiting for seventh-round receivers Charles Johnson (knee) and Kevin Dorsey (hamstring) to get back on the field. Both were hurt on the second day of practice.

"It's kind of weird that I was hurt and he was hurt at the same time" Johnson said. "I mean it's real frustrating. I played all (through) college football and high school football and never missed a practice for injury."