If there is any team that is being overlooked before the season, its the Chargers.
They had a dismal season last year but they did go 9-7 the two years prior under McCoy, this despite playing in one of the toughest divisions in football (Manning was still playing at a high level those two years, Chiefs were very good).
A lot went wrong for them last year, especially with injuries on the offensive line and Allen went down. IIRC, Verrett struggled with injuries last year as well. He should be 100% going into the regular season. Even with the injuries, I don't think they were as bad as their record. They had a lot of close losses against really good teams - Bengals, Packers, Steelers, Chiefs, and Broncos twice. Games with the Bears, Ravens, and Raiders were all one score losses too.
Their offensive line should be a bit better this year, Allen is back and Travis Benjamin will prove to be a good pick-up. Rivers has proven he can ball with just about anyone. Defensively, they added Brandon Mebane, Dwight Lowery, and Casey Heyward. Their CB trio could potentially be one of the best in football (Flowers, Verrett, and Heyward).
I don't think they are going to win the conference, but I think they are kind of underrated.