I think the biggest question mark about the game is the effect of Antonio Gates's absence. Some stats for those who doubt it is significant:
Third down conversions
On third down, Gates caught 30 passes, gaining a first down on 28 of them. Drew Brees completed 72 passes on 3rd down for 54 first down conversions. Gates, with 42% of the 3rd down catches and 52% of the 3rd down conversions, is clearly the go-to guy on 3rd down. Incidentally, SD WR's averaged fewer than 2 catches per game on 3rd down. That's not per receiver, that's the entire WR corps!
Red zone
In the red zone, Gates caught 12 of his 13 TD receptions. Brees threw a total of 20 TD's in the red zone, so Gates accounts for 60% of the RZ TD's.
In Gates's absence, Brees will have to turn to someone, but there is no other Charger that presents the matchup problems that Gates does. Whether McCardell, Parker, or the backup TE can fill the void will be a turning point for the game.