Chargers needs:
OL - Injuries and inconsistency from this unit was probably enough to keep this team out of the playoffs. Fluker regressed, but he should have a resurgence next year with a move inside. Hardaway retired. Chris Watt is young and talented, but he doesn't have much experience as a center. Chad Rinehart is little more than a placeholder at LG. King Dunlap (the team's best and most consistent offensive lineman last year) is a free agent, and re-signing him has to be a high priority. If they can pull that off, they still need a starter at RT. Fortunately, it seems unlikely that Green Bay has much hope of retaining Brian Bulaga. I don't know if Tom Telesco has what it takes to go out and get this guy, but it would be a major coup if he could.
RB - The Chargers will almost definitely let injury-plagued and fumble-prone Ryan Matthews walk. Brandon Oliver looked good for about two or three games, but it seems obvious that he is not the answer for an every day back who may have to make his own holes. There has been a ton of talk about how Adrian Peterson would be such a great match in this offense, but I doubt that the Chargers' front office values him the way that fans and analysts do. This is a position that is easily upgraded through the draft, so I hope they don't spend much, if any, FA money for a tailback.
WR - Eddie Royal is a halfway decent piece of the puzzle, but he's really just a guy. This is another position that I don't think the Chargers need to spend much money upgrading.
DL - The Chargers could really use a big-time pass rusher. However, in a 3-4 defense, the pass rush actually starts with the NT (even if the NT doesn't end up with many actual sacks). The Chargers won't touch either of the overpriced problem children in Detroit. A nice fit might be Denver's Terrance Knighton.
LB - Melvin Ingram and Jerry Attaocho are both young and talented. Unfortunately, neither one of them can stay on the field. The good news is that there are a lot of good 3-4 LBs out there to be had. Cross out Justin houston because the Chargers won't even try to compete for him, but any of the next half-dozen guys would be good additions: Pernell McPhee, Brandon Graham, Jason Worilds, Jabaal Sheard, Arthur Moats, and Brian Orakpu.
CB - Brandon Flowers signed a bottom-dollar one-year/prove-it contract last year and should have made the Pro Bowl. Re-siging him has to be one of the Charger's top priorities. Ike Taylor, Charles Tillman, and Antrelle Rolle are getting old enough to where the Chargers might be able to afford them. Allen Ball and Perrish Cox are other possibilities that could be starters or nickels.