Without him in top form, Indianapolis was a 3-4 team after seven games. With him in top form, the Colts won nine straight and are primed for another playoff run.
For them to go deep into the playoffs, though, the offense must show more balance than it showed during the regular season. For that to happen, Manning needs to be able to correctly read the defense when he comes to the line of scrimmage.
Odds are good that the Chargers are going to come out with two safeties deep. When that happens, Manning will need to know when to audible into a running play and which type of running play to choose.
As the game progresses and — hopefully — the running attack starts to gain some traction, it will again be up to Manning to balance the passing attack with the running game and keep the San Diego defense guessing.
The matchups say that the Colts should be successful on offense, but they still need to execute. That all starts with Manning before the snap.
2. Jeff Saturday: While Manning is busy reading the safeties, Saturday needs to take a look along the line of scrimmage, attempt to determine which pass rushers are coming, where they're coming from, and pass that information along to Manning.
Saturday will need to keep the line calls organized against San Diego
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Although they have certainly improved over the course of the last few seasons against the 3-4 defense — and the fact that a number of teams have switched over to that look as their base defense has helped — the Colts still struggle against it in general and against the Chargers in particular.
The fact that he does not have to worry about Shawne Merriman should make Saturday's life easier, but he still needs to be able to identify pressure and quickly and correctly get that information over to Manning if the Colts offense is going to be effective.
Given the magnitude of the game and the fact that there is no tomorrow, Ron Rivera has probably thought up some exotic looks and will be throwing some things at Saturday that he has never seen before. He needs to be able to adapt and improvise if Manning is to have the time he needs to operate.
3. Robert Mathis: Greg Talmage already broke down the Freeney-McNeil match-up, which looks like it will be a favorable one for Freeney. However, it may not be as nice as the one between Mathis and right tackle Jeromey Clary.
In the Week 12 game, Clary had help from either a tailback or a tight end on most snaps and the Chargers left McNeil to block Freeney one-on-one. After Freeney took advantage of that matchup in the first half, San Diego gave McNeil help and left Clary to block Mathis one-on-one.
Mathis finished the game with two sacks and a forced fumble. Freeney ended it with an assisted tackle. Although Freeney was able to apply pressure in the first half, Mathis was able to get to get the quarterback to the ground in the second half.
In this game, with both players having made the Pro Bowl and performing at their usual high levels, the Chargers will have to pick their poison: Freeney, Mathis, or keeping seven men in to block four.
None of those options is a pleasant one for San Diego, but, if they decide to favor Freeney's side, Mathis needs to make them pay like he did in November.
4. Chad Simpson: Both as a reserve for Joseph Addai and Dominic Rhodes that can add a little bit of a burst and change of pace in the running game and as a kick returner, Simpson has his biggest chance yet to have a profound effect on a game.
Simpson could give the Colts a field position boost
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The Colts will need to run the ball and run it well. They have not been effective running the ball all year, ranking 31st in the league and averaging 79.6 yards per game. If Addai and Rhodes struggle early, Simpson and his speed to the perimeter might be just the shot in the arm the running game needs.
On a team that has averaged an atrocious 20.8 yards per kickoff return this season, anything that Simpson can add as a return man is only going to help this team. They won 12 games without field position on their side. In the playoffs, where everything intensifies and you need to find every advantage and catch every break you can, Simpson can give a the team a huge boost by adding five or ten yards to that average. And, in a tough playoff matchup on the road, every boost helps.
5. Kelvin Hayden: Hayden draws Vincent Jackson, which will make for a tough evening for him no matter how healthy (or not) Antonio Gates and LaDanian Tomlinson are. With Gates and Tomlinson either on the sidelines or hobbled due to injury in the Divisional Round playoff game last season, Jackson delivered as a go-to guy for Philip Rivers and Billy Volek, catching seven passes for 93 yards and a touchdown.
On the other side of the field, Chris Chambers has been injured and very inconsistent. Jackson has emerged as the lead playmaker in a surprisingly balanced passing attack, having posted the only 1,000 yard season of any receiver on the team.
If Gates and Tomlinson are slowed by injuries on the field, or relegated to the sidelines, Rivers will be looking for Jackson in key situations. Hayden needs to make sure that Jackson is unavailable when Rivers looks in his direction.