Start Ladarius Green
The Jacksonville Jaguars are notorious for not being able to cover TEs. That probably means you should start both Antonio Gates and Ladarius Green, but Green should have the better day without much of a run game to pull the front-seven away from Gates' favorite spot on the field. Expect one or two big plays, and probably a touchdown.
Sit Donald Brown
If you picked up Donald Brown in hopes that he'd be Ryan Mathews, Danny Woodhead, or some combination of the two, you're sorely mistaken. If he's going to have a good game, it's likely going to be against a team that has a strong passing defense that forces the Chargers to run the ball. That's not the Jaguars.
Start Philip Rivers
Sit Toby Gerhart
I feel weird for saying this, because Gerhart is exactly the type of RB that has given the Chargers fits in the last few years, but this year's Charger defense is fast and has been quite good at tackling. Don't expect Toby to get those broken-tackle big gainers that he would have last year.
Start Blake Bortles
San Diego has zero interceptions this year, and Bortles will likely be throwing a lot to try and get back into this one late. John Pagano has a history of going into a soft zone in those situations and letting QBs pile up good stats. I would not be surprised if Bortles finished this one with 250+ passing yards, a couple of touchdowns, and zero turnovers.