RB Chad Simpson
Simpson will face a stiff challenge on Sunday against the very athletic and active front seven of the Titans, no matter if they choose to play their reserves, since they have so many injuries along the defensive line.
He will need to accelerate into the crease and make yards before and after contact in order to show opponents, the coaching staff, and fans that Indianapolis has someone that can step in and gain the yards on the perimeter that Addai usually eats up.
Dominic Rhodes has proven to be effective between the tackles, but Simpson is the only back remaining on the roster that can pick up yardage in chunks outside the tackles if anything should happen to Addai.
With Addai's health in question, Simpson needs to step up in this regard to give playoff opponents something else to game plan for in the event that Addai cannot go.
2a. Marcus Howard and b. Curtis Johnson: Hopefully they will only need to flash their speed and explosiveness as a testimony to the fact that the Colts can identify good pass rushers at any point in the draft process.
However, since Robert Mathis and Dwight Freeney have only been fully healthy for a small percentage of the season, Indianapolis may need to depend on these two rookies more as the season stretches on into January and hopefully beyond.
They need to prove that they have a strong grasp of the system that Tony Dungy and Ron Meeks have been running so well for so long, not only in terms of pass rushing technique, but in run support.
The more these two young men show on Sunday, the less emboldened Colts opponents will be if Freeney or Mathis go down with an injury at some point during the postseason.
The more Richard can accomplish, the more at ease everyone can feel. He stepped in and performed well earlier this season, but, as the pressure continues to mount and the games become more important, his mettle will be tested more and more.
How he responds on Sunday, after a preseason and early season that had its fair share of hiccups, will be crucial in determining how ready he might be for prime time.
4. Keiwan Ratliff: Everyone has seen how he has reacted as a role player and sub package guy in this defense, but being "the guy" is an entirely different ball of wax.
Ratliff has obviously excelled when given certain responsibilities in the passing game in known passing situations, but how he will respond when asked to come up in run support, or cover his responsibilities when a pass is not expected is something else entirely.
When the pressure rises in January, the Colts coaches will need to know what they have in Ratliff. Sunday gives them an excellent opportunity to test him in a controlled environment before they may need to count on him if numerous cornerbacks go down with an injury, as has been known to happen in this and other seasons.
5. Jim Sorgi: Everyone from Bill Polian to the fan sitting in row EE has thought of what life — and the Colts offense — would be like without Peyton Manning. They were all given a glimpse of that reality during the preseason in 2008 and in last season's finale against the Titans.
The hope, of course, is that no one tied to the Colts will have to deal with that reality for some time. However, Sorgi can allay some of those fears with a strong performance on Sunday after Manning takes a seat.
Sorgi has proven unable to put the mass paranoia surrounding a non-Manning Indianapolis offense to bed as of yet, but that does not mean that he does not have such a performance in him. A strong relief performance will put the rest of the league on notice that the Colts do not need their laser rocket-armed quarterback to be effective.
A weak performance will only further the notion that as Peyton Manning goes, so go the Colts.