The positive part of the offensive line's 2012 performance was from the two starting tackles Jordan Gross and Byron Bell. They made 31 starts between them and though Bell didn't grade out in the positive he did show improvement from his rookie season.
Ranking the 2012 Offensive Lines | ProFootballFocus.com
27. Carolina Panthers (9) PB – 27th, RB – 23rd, PEN – 14th
Stud: As is often the case, it’s the ever reliable Jordan Gross (+16.4) who continues to get the job done, even if his performance in Week 17 was the worst we've ever seen from him. He may never be an elite tackle, but at least he’s more than a one-tricky pony.
Dud: There was a close competition but ultimately the inability of Geoff Hangartner (-14.5) to get any push in the run game meant he was the way to go.
Summary: The Panthers haven’t been shy about investing draft picks on the line, but with the injury to Ryan Kalil this year it fell apart. Amini Silatolu looked every bit the rookie, while Byron Bell isn’t good enough, often enough, to be a starter in this league yet.
Sticking with the tackles let's get to the grades:
LT Jordan Gross
As you can see by PFF's rankings Gross had another nice season even if it wasn't quite Pro Bowl caliber. Gross remains durable and the Panthers best offensive linemen in spite of his advancing age (32). Though he has a high cap value in 2013 I think the Panthers would be wise to do what it takes to keep Gross in uniform for another couple seasons. He seems up for it and still has enough skill to play at a high level.
RT Byron Bell
On the other side of the line from the Pro Bowl former 1st round pick Gross we have the 2nd year UDFA Byron Bell. As pointed out above though Bell didn't light it on fire he did improve in 2012, especially in the area of run blocking. He still struggles at times with speed rushers but typically if he can get his paws on a guy he handles him. At 6'5" 340 lbs no one is going to bull rush Bell but he can be beaten to the edge. Another plus is Bell has 27 starts in 31 games in his first tow seasons providing the kind of durability needed on the edge. The Panthers did try Bell at RG for a game trying to get their best players on the field but quickly moved him back to RT when Garry Williams struggled on the edge.
Williams went from back-up to starter once the injuries started to pile up. Williams started at RT against the Giants and Cowboys only to kick inside to RG for the last seven games of the season. The fact he didn't last long at RT should tell you what we need to know for the purpose of this post. Though his RT ranking may could out low I think Williams has a real shot at being a key back-up if not starter at RG in 2013.
Campbell came to Carolina in a preseason trade with the Raiders for RB Mike Goodson which at this point has been a very one-sided deal towards the Raiders. I would love to give Campball a grade but the guy was inactive for 10 games, only seeing game action the last two games against the Raiders and Saints. In the Raiders game he replaced the injured Amini Silatolu at LG. Campbell is a bit of an enigma at this point, seeming to have all the tools to be a starting tackle in this league but just can't get on the field. I really don't know if he has a future in Carolina in 2013 or not.