One of the Vikings strengths this year has been their ability to make big, momentum changing plays. They're currently second in the NFL with a +14 big play differential, and have had 30 big plays so far this season, also the second most. Of those 30 big plays, almost all of them have been made by the defense, which, considering how inert the Vikings pass game is, is not all that surprising.
The Vikings are going to need both their defense and their passing game to make big plays if they hope to upset the Chargers on Sunday. Defensively, the Vikings best hopes for a turnover will come when Philip Rivers drops back to pass. Rivers has ten turnovers so far this year, having thrown seven interceptions and lost three fumbles. He's also had two of his fumbles recovered by the Chargers as well. If the Vikings can get pressure on him, he'll give them the ball. The fact Cory Withrow will be playing for the Chargers will help the Vikings' pass rush, but if Antoine Winfield isn't on the field, it will probably be a moot point anyway, as he's one of the few defenders that the Vikings count on to help stop both the run and the pass.
The Vikings' defense isn't really likely to be what it decides the game, however, just like it hasn't been the deciding factor in any game so far this year (except for the Atlanta game). What it will come down to is the Vikings' ability to move the ball on offense, which means it will come down to their ability to pass the ball. The Tarvaris Revolution cannot be held down, and he'll be starting on Sunday.
And you know what? Contrary to what I said earlier this week, Tarvaris Jackson should be starting every game that he is healthy enough to play in. The Vikings are not making the playoffs this year, so it doesn't matter whether Kelly Holcomb or Brooks Bollinger gives the Vikings a (slightly) better chance to win. What matters is gathering enough information on Tarvaris to find out whether he is the quarterback of the future. If he's not, he's not, and the Vikings will have ample opportunity to find the quarterback of the future in the draft. If he starts hitting open receivers and learns when to take off, then he is. Either way, nine games of the Tarvaris Revolution should give the Vikings all the information they need to make the decision.
[If you're interested, Football Outsiders has a nice breakdown of the play that resulted in Visanthe Shiancoe's first touchdown catch for the Vikings]