The Packers are set at middle linebacker for the next few seasons with 26 year old LB Nick Barnett, assuming his disorderly conduct charges are resolved this offseason. On the field he has been very consistent during his five seasons, and he's just a step away from making a Pro Bowl. He's a similar player compared to Seattle's LB Lofa Tatupu, who started for the NFC in the 2008 Pro Bowl, in terms of his ability to fight through tackles and in pass coverage.
LB A.J. Hawk statistically regressed in 2007 with fewer tackles, pass defenses, sacks, and interceptions then in 2006. The NFL's top outside linebackers usually have high sacks totals, much higher than the 4.5 he's recorded in his first two seasons, but the Packers rarely let Hawk blitz. Despite the statistical decreases, he did play better in his second season. He's been solid against the run since day one, but his weakness was in pass coverage. But as the 2007 season wound down, the Packers played better in pass coverage against tight ends and running backs then they had over the previous few seasons, and Hawk played a large part in that improvement. He just finished his 2nd NFL season while playing at age 23 (he turned 24 last month) and he's still likely to get better.
LB Brady Poppinga might seem like the weak link at linebacker, but the Packers don't ask too much from him either. As the 3rd linebacker, he comes out whenever the nickel back comes in, so he's essentially a reserve player while technically a starter. He isn't great in coverage and occasionally has a bad tackle or bad special teams play, but he's generally solid against the run which is the most important skill he should possess. The Packers could make a move in free agency or the draft to upgrade at his position, but it would cost a lot of money or a high draft choice to fill a part-time position.
The biggest concern is that it is a giant step off a cliff from Barnett and Hawk to the next linebacker on the roster. LB Abdul Hodge was drafted in the 3rd round in 2006, but injuries have probably ended his career while technically he's still on the roster and hopes to return in 2008. LB Tracy White was usually the only linebacker active each week besides the starters, but his role is on special teams and he didn't shine too bright when given a lot of playing time last preseason at outside linebacker. LB Desmond Bishop is the backup middle linebacker, but the 2007 6th round choice is no future star and would only be an adequate stopgap. It would be a good idea for the Packers to spend a mid-round draft choice to give the team some depth.