Without going into a whole list of the Chargers free agents (although I will do that in the near future) the list of potential franchise tag candidates is fairly small. They are: Mike Tolbert, Nick Hardwick, Antonio Garay, Jacob Hester and Jared Gaither. Let's go through them one at a time.
The San Diego Chargers have used the Franchise Tag each of the last 3 years. The first two of those years the team used it on RB/KR Darren Sproles. Then last year the Chargers slapped it on WR Vincent Jackson and let Sproles walk. The Franchise Tag requires the team to offer a player a one year contract that is the average of the top 5 salaries at the player's position or 120% of the player's salary from the previous season. So, if the Chargers wanted to use the Franchise Tag on Vincent Jackson again, they'd need to offer him a 1 year contract worth 120% of what he made last year.
That $13 million price tag is probably too much to pay Vincent Jackson and still have enough to do what they need to do sign some other players this offseason. However, the deadline for using the tag comes on February 25 while free agency doesn't start until March 5. The Chargers can negotiate a long term deal with Vincent Jackson at any time before the 25th of February, but once that date passes Jackson (and his agents) know they can get to Free Agency unencumbered and will want to test those waters for the best possible deal. Hopefully, if you have been paying attention, you get the same ticking clock visual that goes with this situation. The Chargers have about a month and a half to resolve this situation with Vincent Jackson.
Recently, the the rumor mill has stated that the Chargers will not use the Franchise Tag on Vincent Jackson. This is either a show of good faith towards the big wide receiver or it's a partial leverage killer. It would seem to be the latter since #83 has said that he'd be okay being re-tagged. Still, if the rumors are true then it begs the question: Should the Chargers use it on someone else?
The roly poly RB is not a starter on the team and is nowhere near the dynamic runner that Ryan Mathews is. Still he's a pretty popular player as evidenced by our approval poll last year and he has his uses both on offense and on special teams. Tolbert won't exactly be a high demand free agent and the difference between the cap hit that comes with signing Tolbert and paying for the tag are too big. It's also a fungible position, Tolbert is not the main guy and the team could take an even smaller cap hit by just replacing Tolbert with someone who's almost as good, but less experienced.
The incumbent Center is an interesting case. He's getting up there in age so a one year deal would be appealing. He's also likely to be in demand since he's one of the best in the game at his position. However, he's also at a point in his career where he'd probably like a contract that takes him through the end of his career. So, a 3 year deal or so works for both player and team as it saves some cap space.
The Nose Tackle position is one of the most important positions in the 3-4 and Garay has been holding it down for the Chargers for the past two years. That being said, he's in his 30s and the team already has his replacement in house in Cam Thomas who played well down the stretch. He might not even be the starter if he returned. It's better to take the risk of him signing elsewhere and not risk paying for an expensive backup in 2012.
The organization loves Hester, both for his work on offense and on special teams. He also plays FB, which isn't a position with many high paid players. However, according to Franchise Tag rules FBs get paid like RBs so that doesn't help. No way it's worth it to pay at least $8 million for what Hester does.
Charger fans are getting familiar with Gaither as he stepped in late this season and filled in admirably for Marcus McNeill and was a massive upgrade over Brandyn Dombrowski. A show like that will put him in demand among teams that need an offensive tackle. It might be the case that only the Franchise Tag will keep him in San Diego and the Chargers might want him because of lingering questions about McNeill. However $10 million is probably too much for that kind of peace of mind.
Conclusion: It's Vincent Jackson or bust. Signs point towards the Chargers passing over Jackson for the tag and just keeping it in the pocket for the season. If they do that, I hope this article helped you understand that rationale.