The San Diego Chargers finished this past season on a strong run that saw them making it to the Divisional Round of the AFC playoffs.
The team has lost their lauded playcaller in Ken Whisenhunt, who was hired by the Tennessee Titans to be their head coach, but anyone who watched the Chargers' loss to division rival Denver in the playoffs knows that Whisenhunt's play-calling wasn't always all that great anyway.
Much more important for this team is keeping their nucleus together, and although the team has only a few pending free agents, there are still players that this team just cannot afford to lose right now.
Chad Rinehart, Guard
Chad Rinehart has had some injury concerns and in general, had a decent season this past year while not being anything close to a world-beater at the guard position.
However, the Chargers are just a year removed from one of the absolute worst offensive lines in the league, and it's been seen how Philip Rivers performs when he doesn't have a good line in front of him. Rinehart's best season came in 2011, when he ranked ninth among guards on ProFootballFocus.
That year, he started six games at left guard and nine games on the right side of the line; this most recent year was no different, when he started four games at right guard and seven games on the left side. Rinehart is no longer the player he used to be, but continuity is extremely important along the offensive line, especially with a player who is versatile enough to line up on either side of the line. The 28-year-old guard is a solid player and his loss would be unfortunate for the San Diego Chargers.
Donald Butler, Inside Linebacker
Donald Butler had a poor season, but in the two years prior he proved to be a pretty solid run defender. He's not an amazing linebacker, but again, continuity is always very important for an NFL team, and linebacker is one of the key units on the defensive side.
The team should probably look to upgrade on Butler, but at this point, the team has other, more pressing needs (such as in the secondary and along the interior offensive line), so I think the Chargers just need to roll with Butler for another season at the least before looking to move on at inside linebacker.