As the Indianapolis Colts prepare for their second preseason game Sunday at Pittsburgh), their roster is starting to take shape. They do still have some holes to fill -- especially on defense -- but there were lots of positives in their 38-3 win over St. Louis. Though it's early in the preseason, there were still some impressive performances that may have earned some guys a leg up in the race to fill up the roster. Each week we'll examine how the team is shaping up, and who seems to have the best chance of making the 53-man roster.

QB -- In (3): Andrew Luck, Drew Stanton, Chandler Harnish. Out: none. Analysis: Well, Luck will probably make the team. In fact, barring any moves to add another quarterback, these three are safe. Harnish is a local product, and both he and Stanton looked sharp in the opener.

RB -- In (4): Donald Brown, Mewelde Moore, Vick Ballard, Delone Carter. Out: Darren Evans, Deji Karim. Analysis: Brown, Carter, and Ballard all looked solid in Sunday's game, and Moore will probably hang on given his relationship with offensive coordinator Bruce Arians from Pittsburgh. Karim and Evans, though solid, have similar builds to the others, so it will be difficult to crack that four-man rotation. The Colts are expected to bring on a few free agent backs, as well.

WR -- In (7): Reggie Wayne, Austin Collie, LaVon Brazill, T.Y. Hilton, Donnie Avery, Quan Cosby, Griff Whalen. Out: Jeremy Ross, Kris Adams, Jarred Fayson, Jabin Sambrano. Analysis: A lot of newcomers at the position, and Hilton and Brazill were impressive Sunday and have been throughout camp. Whalen sat out with an injury, but he could be a factor given his relationship with Luck, since the two of them played together at Stanford. This may be the most fluid position from week to week, as Whalen and Cosby are precarious, at best.

TEs -- In (3): Coby Fleener, Dwayne Allen, Dominique Jones. Out: Kyle Miller, Andre Smith. Analysis: Fleener and Allen are rookies expected to make a big impact right away, and Jones was used in short yardage situations out of the backfield against the Rams, perhaps cementing his roster spot.

OL -- In (11): Anthony Castonzo, George Foster, Jeffrey Linkenbach, Joe Reitz, Samson Satele, A.Q. Shipley, Mike McGlynn, Seth Olsen, Winston Justice, Mike Tepper, Justin Snow. Out: Ty Nsekhe, Jason Foster, Zane Taylor, Hayworth Hicks, Steven Baker, Justin Anderson, Matt Overton. Analysis: The Colts have already experienced some injury trouble, losing OG Ben Ijalana, who was projected as a starter. McGlynn is currently out with a high ankle sprain, which could give others a chance to compete. Snow will be kept on as the long snapper.

DL -- In (6): Cory Redding, Antonio Johnson, Fili Moala, Ricardo Mathews, Brandon McKinney, Drake Nevis. Out: James Aiono, Chigbo Anunoby, Jason Shirley, Josh Chapman. Analysis: With the new 3-4 front, the Colts will be forced to be deep at linebacker rather than on the line. They have some solid run stoppers, and Redding -- who was out with an elbow injury Sunday -- is a solid rusher off the edge.

LB -- In (9): Robert Mathis, Kavell Conner, Dwight Freeney, Pat Angerer, Jerry Hughes, Mario Harvey, Jerrell Freeman, Justin Hickman, Larry Lumpkin, Tim Fugger. Out: Scott Lutrus, Greg Lloyd, Mario Addison, Jerry Brown. Analysis: This is an especially tough position to predict at the bottom, since most guys will be battling for special teams spots. Fugger has been out with injury early, but should get a chance later in camp, especially after Scott Lutrus was lost for the season. There will be opportunity to rise now that starting MLB Pat Angerer will be out six weeks with a broken foot.

DB -- In (8): Jerraud Powers, Justin King, Tom Zbikowski, Antoine Bethea, Cassius Vaughn, Korey Lindsey, Brandon King, Chris Rucker. Out: Jermale Hines, Joe Lefeged, Mike Newton, Terrence Johnson, David Caldwell, Cameron Chism, Buddy Jackson, Antonio Fenelus, DJ Johnson, Matt Merletti, Latarrius Thomas. Analysis: The Colts secondary struggled mightily last season, and only Bethea, Powers, and Zbikowski are assured spots. Justin King and Vaughn will battle for the corner spot opposite Powers, but there is a lot up for grabs.

Special teams -- In (2): Adam Vinatieri, Pat McAfee. Out: Brian Stahovich. Analysis: This will likely remain unchanged.

For more up-to-the-minute news and analysis from Colts blogger Evan Hilbert, follow @CBSSportsNFLIND