of all the backs that the Saints have had the last few years, only thomas was a low investment.  They have had a lot of talent in their back field.  Sproles and Bush are comparable IMO.  Both great recivers out of the back field, but I've never liked either running the ball a lot.  
  McCoy and Charles I find comparable to each other, the opposite of the first two.  Great runners, not so great recivers. 
  CJ we have seen excel at both.  I'm excited for a healthy CJ this year.