Well well well, the Colts went from one of the thinnest backfields in the NFL to one of the deepest in one off-season.  Let's take a look at who we have and then I'll suggest who we keep.

Joseph Addai - while no introduction is necessary, this player could certainly use someone who can spell him more often than KK was capable of doing last year.  Primary problem with KK as a back-up, we like to have a pass-catching RB option in on most of our offensive plays, this limited KK's time in the line-up and resulted in Addai getting a lot of carries.

Kenton Keith - Say what you will about KK's pass-catching abilities.  Last year he was a solid back-up RB.  There is no reason to believe that he will not improve in his second year and there is no doubt the man can run hard.  Whether or not he'll significantly prove as a pass-catcher is yet to be seen.

Dominic Rhodes - While Dom has had his share of off-field problems, while he was in Indy he seemed really happy.  His teammates loved him and will certainly be excited about his return.  For the price we got him, it was a no-brainer to bring him in.  Rhodes is used to the concept of backing up Joseph Addai, grew close to Addai as he welcomed him into the league in 2006, and is a strong pass-catcher out of the backfield.  In Rhodes the Colts have secured a back-up who knows their offense, fits well in the offense, and has the legs left to be called on significantly during the regular season should it be necessary.

Mike Hart - While Hart has yet to prove whether he can play at an NFL level, there is no doubt  that he is one of the most exciting prospects the Colts have gotten in the 6th round in recent memory.  In the Coltpower fan poll on the draft, Hart received 98% support from all those voting on whether or not they liked the draft choice.  If Hart does show his skill in training camp, having him on the roster would make us one of the deepest teams at RB in the league.

Chad Simpson - In terms of something to prove, Simpson is probably the biggest long-shot to make the team.  However, the kid can flat out run.  He's a faster option than Hart and did some good things but played against a much lower level of competition than Hart.  It'll be interesting to see how he pans out but he may only have a shot at the practice squad... at least for this season.

Clifton Dawson - Unless Dawson has done something over the off-season to drastically improve, I don't see him making the roster.  If he plays at a higher level than Chad Simpson he could make the practice squad but the Colts have added A LOT of talent at the RB position going into training camp this year and that makes Dawson's job that much harder.

Luke Lawton - Luke Lawton did a decent job as a lead blocker when we used one, which was rare.  He also played a role on special teams, though he wasn't a standout in this area.  As a result, Lawton may well lose his roster spot before the regular season.  I know some Colts fans will moan and complain about his ability to be our only true fullback.  I say... so what?  Our offense rarely if ever has a lead blocker... and if we really need one the value of having a lead blocker was so small that we even lined up a DT in Dan Klecko to do the job.  Why not use D. Clark or another player with the capability to fill multiple roles in those situational spots and keep your top talent at the RB position.  So... unless Hart/Simpson are both flops... I really don't see Lawton sticking around.  Practice squad maybe but he'll be competing for that spot.

Justice Hairston - I know we have him but know little more than that.

I will restate - I see no reason to not have a roster which includes the best talent available coming into the regular season.  As a result I can't help but drool over this backfield:

Joseph Addai
Dominic Rhodes
Kenton Keith
Mike Hart

That my friends may be the deepest backfield in the league.  Replacing any of the players above with the other players I mentioned, in my estimation, is decreasing total value at the RB position.  The best argument could be made for Lawton but I've already talked about his limited value.  The only way that list would change, based on all information I have right now, is if Chad Simpson is better than Mike Hart.  It's possible but I just doubt it.