After an 0-2 start to the season, including a disappointing home loss to the lowly Browns, the Colts are dealing with continual changes to a roster that is already starting to get nicked up. Safety Melvin Bullitt went down Sunday but managed to come back into the game. In many ways, his return did nothing to help Indianapolis stay in a close game. Still, he joins a list of key players who may have to miss time. With news hitting that the Colts signed second-year safety Stevie Brown, and Jim Caldwell admitting that Bullitt has suffered an injury that seems to leave his future in doubt, it's entirely possible that there will be a new starter at strong safety against the Steelers Sunday night. "Next man up," and "new starter," is the type of thing Colts fans became all too familiar with in 2010, and sick to their stomach about Week 1 this year when Peyton Manning missed a start for the first time in his career. The team cannot afford to lose players at the pace it did in 2010. With Peyton Manning already off of the field, the rest of the team's leaders will be needed to keep things together long enough for a potential Manning return in 2011. The good news on Manning is that he took the practice field today for some light cardio, suggesting that he is beginning the process of conditioning for a return. Gary Brackett and Ryan Diem are both possible scratches for the Sunday night game, as coach Jim Caldwell expressed that their situations were "uncertain" and "up in the air," respectively. If Diem is unable to go, Coach Caldwell indicates that Mike Pollak will play in his place. In order to protect the team's depth, linebacker Nate Triplett was re-signed to the team last week (following injuries to Brackett and Ernie Sims) -- tight end Mike McNeill was dropped and subsequently added to the practice squad to make room. Fourth running back Darren Evans was dropped this week in order to make room for Stevie Brown, and it was confirmed today that he was signed to the team's practice squad in place of wide receiver Marshall Williams. The early season struggles put a lot of people on the hot seat, no one more than Coach Jim Caldwell. He acknowledged his situation and took responsibility for the team's early struggles earlier today when he was asked if he said he thought it was obvious that he wasn't doing a good job getting the team ready to play. With the offense still struggling to find a rhythm, the defense will have to continue progressing. Losing Brackett and Sims certainly hurts pass coverage over the middle of the field though, and will require a quick learning curve from second-year linebackers Kavell Conner and Pat Angerer who are far superior run defenders than they are at playing passing lanes. After years of having one of the league's best offenses and a defense that has been picked on by pundits for being too small and incapable of stopping the run, the resolve is still there. Members of the defense insist they will ignore such suggestions and continue working hard to turn things around. Before Manning returns, they will have to do that if they want any hope of a playoff berth. The Pittsburgh Steelers know not to sell the defense short though, as Dwight Freeney and Robert Mathis still demand a great deal of respect from opponents who intend to keep a quarterback upright. Ben Roethlisberger has taken a lot of hits over the last few seasons and took a beating against the Baltimore Ravens. He was wise to pay the duo lip service and to recognize that the two are particularly disruptive indoors. This game will be a huge test for a defense that showed signs of improving against the run against the Browns. The Steelers are a more balanced offense that will almost certainly make it to the playoffs and contend for another shot at a Super Bowl. These guys are going to have a really busy week.