In his PC, Tomlin said Davenport and Russell will carry the load. He also said he didn't even know if Haynes will suit up or not. He did say that Haynes is a good 3rd down RB though, but never specifically said if he would come in and play on 3rd downs. As I said though, he doesn't even know if he'll suit Haynes up or not against the Ravens. He said he'll know a whole lot more about the teams situation as a whole and who's going to suit up and who's going to play against the Ravens after the Chargers/Broncos game depending on what happens.
Personally, I'm hoping to see Davenport, Russell, and Davis all getting carries against the Ravens, obviously with Davenport carrying the load, though with Russell getting a few carries here and there and Davis also getting a couple of carries possibly in short yardage situations.