10. Nathan Vasher
San Diego's biggest free-agent pickup, Vasher is the frontrunner for the team's nickel back position. He's coming off a couple down, injury-plagued seasons in Chicago, but the hope is that a healthy body and a fresh start will help him recover his Pro Bowl form.
9. Kris Wilson
Wilson moves up a rung on the ladder thanks to the offseason departure of Brandon Manumaleuna. This should provide a few more chances to catch the football -- he caught just four passes in 2009 -- but his biggest contributions will come as a blocker and on special teams.
The Chargers will lean heavily on a rotation of journeymen on the defensive line, but Martin is the exception. He is an outstanding athlete and has the potential to emerge as a difference-maker. Martin made terrific strides throughout his rookie season and will have to do so again in 2010 to earn playing time on a deep unit.
Despite the addition of third-round pick Donald Butler, Siler will play an important role for Ron Rivera. He's the team's best run-stuffing linebacker and is the driving force behind a stingy goal-line defense. He will also lead the way on special teams, an increasingly important role now that Kassim Osgood is no longer in the picture.
6. Billy Volek
Volek is the toughest player to rank on this list. On one hand, it's a mistake to undervalue the worth of a proven backup quarterback, especially one who has shown he can step in and win big games. On the other hand, the Chargers know that if Philip Rivers goes down, so do their Super Bowl aspirations.
5. Paul Oliver
The numbers don't lie: Oliver is an ascending player. He finished last season with three times as many tackles (49 to 15) and pass breakups (three to one) as he did the season prior. Now, he must continue to progress in a safety corps that's as crowded as any spot on the team. If he can do that, he has a chance to establish himself as the team's top reserve defensive back.
The Chargers got a taste of Mruczkowski's value when he started 13 games last season in place of the injured Nick Hardwick. Entering his sixth season, the versatile Mruczkowski provides depth across the interior offensive line and can even give some snaps at right tackle in a pinch.
After catching just eight balls in each of his first two seasons, Naanee showed much improvement in 2010 by recording 24 catches for 242 yards and two scores. He will have even more opportunities in his fourth campaign, as he enters as the No. 3 receiver, a role he didn't inherit until Week 9 last season.
Sproles is not a starter, but he's certainly paid better than most of the starters on the team ($7.29 million). He's been worth every penny up to this point in his career, providing electrifying plays as a kick returner and a receiver out of the backfield. The addition of Ryan Mathews should help Sproles continue to flourish, as he can remain in his role as the ultimate change-of-pace back.
English had a quiet rookie season, posting just two sacks, but the Chargers coaches are still very high on him. He needs a significant sophomore surge, however, as the Chargers can't go another season with just 15 sacks from the outside linebacker position. If English realizes his potential, it will spark San Diego's pass rush and ensure that English does not appear on any non-starter lists next offseason.
Michael Lombardo is a member of the Pro Football Writers of America and 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 15 years and covered the team since 2003. You can see more of his updates by following him on twitter.