Start: Antonio Gates, TE
It really doesn't matter how many other variables you change, if Philip Rivers gets a pass rush on him, the first thing he does is look for Antonio Gates. It happened against the Arizona Cardinals and you be sure it will happen again against the Seattle Seahawks, who have an even better secondary. Gates may not get another touchdown and he likely won't have any big plays, but expect him to lead the team in targets.
Sit: Keenan Allen, WR
If you drafted Keenan Allen, you will be a happy fantasy football owner and San Diego Chargers fan this year.... after this week. Allen has drawn the two best CBs in the league in the first two games of the season, but he'll spend the rest of the year with the upper-hand (depending on how you feel about Darrelle Revis). This should be the last non-bye week when Allen isn't in your starting lineup.
Start: Marshawn Lynch, RB
Beast Mode should have a field day against a weak Chargers front-seven and a team that is known for its poor tackling skills. He lives for those plays where he can break two tackles and run for a long TD, and the Chargers defense gives those type of plays up to guys with half of Lynch's skills. With Christine Michel out with an injury, Lynch will get even more chances to get in the end zone.
Sit: Percy Harvin, WR/RB
After seeing how he obliterated the Green Bay Packers in Week 1, and looking at the rest of the weapons in the Seattle passing game, I'm certain that John Pagano's plan is going to be to take away Harvin with double-teams and force someone else to step up. This being the Seahawks, they will have no issue with taking better opportunities elsewhere on the field.