Colts just released the first depth chart. Cassius Vaughn is currently the starter across from Powers but I bet that changes in a couple weeks when everybody makes the cuts to 53. I think we'll probably replace half our defensive backfield with whoever the Eagles and the Ravens cut. Here's the whole depth chart at the moment, according to Mike Chappell (via Twitter):
1st depth chart: LT Castonzo, LG Linkenbach, C Satele, RG McGlynn, RT Justice, WRs Wayne/Collie, TEs Fleener/Allen, RB Brown, QB Luck
Defense: LE Redding, NT Johnson, RE Moala, SLB Mathis, MLB Conner, WLB Angerer, RLB (rush LB) Freeney, LC Vaughn, RC Powers FS Bethea, SS Zbikowski. Returners: KR and PR Brazill.
Key backups with depth chart: WRs Avery, Brazill; RB Moore (not Carter or Ballard); NT McKinney; LC JKing, RC Lindsey; SS Hines.