Later in the 6th round, and in round 7, the Colts used their compensation pick to address more defensive backfield depth and special teams.
Round six, pick #207: Antoine Bethea, S Howard
Round seven, pick #238: T.J. Rushing, Return Specialist, Stanford
It's not often that guys from these rounds make the team. However, there are always expections. Raheem Brock was a 7th round pick for Philly. The Colts picked him up immediately after Philly cut him in 2002, and Brock has blossomed into one of the best Colts defensive linemen.
Beathea offers more depth at safety, and he will most likely play special teams if he makes the team. Rushing could be a diamond in the rough. The loss of Troy Walters to Arizona and Dom Rhodes' new responsibilites running the ball have both left voids in the return game. The Colts were putrid last year returning punts and kicks. If Rushing can utilitze his speed, he could be the strong return specialist the Colts need.
So, after analyzing each pick, I guess I have to assign some sort of "draft grade." I personally think draft grades are silly and they mean nothing. People gave Washington high marks for drafting Lavar Arrington back in 2001. By default, the Colts should automatically get a B+ grade, because they have never had a bad draft since Polian arrived in 1998. The only reach pick I can think of is Rob Morris in 2000.
So, for this draft, I'll give the Colts a B+, and I'll assume that four players in this draft will either start next year or play significant roles for the team.