Luis Castillo and Antonio Garay both have contract offers on the table. Castillo is the better player of the two, especially after Garay regressed last season, but Garay fills a bigger need since the only other veteran nose tackle on the roster is Cam Thomas.
Castillo missed most of the 2011 season after breaking his leg in the season-opener. His absence hurt the run defense, which slipped to No. 20 after ranking No. 4 in 2010, and also impacted edge rushers like Shaun Phillips, who rely on Castillo to occupy blockers and free up rushing lanes.
Although not statistically impressive (Castillo has not topped 2.5 sacks since 2006), the former first-round pick started an average of 15 games between 2008-2010. His return, along with the pick-up of OLB Jarret Johnson, would go a long way towards toughening up San Diego's defensive front seven.
NT Antonio Garay
Garay can still be a productive player when his snaps are limited, ensuring he remains healthy and fresh. If he returns to join Thomas in the mix, the Chargers can feel good about the middle of their defense. If Garay defects, nose tackles becomes a draft-day priority.
If Castillo and/or Garay signs elsewhere, it increases the odds the Chargers bring back DT Tommie Harris. Harris was signed as an injury fill-in last season, thanks in large part to his familiarity with defensive line coach Don Johnson, and he exceeded expectations. He recorded three sacks in the second half of the season and became a key cog in the defense's third-down packages.
Harris was first seen as a poor fit in a 3-4 scheme after spending most of his career playing the three-technique in four-man fronts. But he fit in well enough to prompt the Chargers to release promising youngster Ogemdi Nwagbuo to preserve Harris' place on the roster.
As for Harris' place on the 2012 roster -- as well as the spots for Castillo and Garay -- that will be determined in the next month. Castillo and Garay have to become the first dominoes to fall. If they are still standing come draft time, the Chargers will find some new toys to play with.
Which D-lineman do the Chargers need back most? Discuss in the message boards.
Michael Lombardo is a long-time contributor to the Scout.com network. His analysis has been published by the NFL Network, Fox Sports and MySpace Sports. He has followed the Chargers for more than 16 years and covered the team since 2003. You can see more of his updates by following him on twitter.