Colts beat writer Mike Wells was asked who would have a bigger role at running back this week - Dan Herron or Trent Richardson:
I'm going with Dan Herron. He spent most of the season as the Colts' third running back, then moves into the starting lineup against Jacksonville and rushes for 65 yards and has 31 yards receiving. Richardson, who everybody has been waiting to see get going, rushed for 42 yards and didn't have any catches out of the backfield.
The thought was coach Chuck Pagano started Herron over Richardson because Richardson missed a day of practice because he was sick. Turns out Pagano went with Herron because he outperformed Richardson in practice. I wouldn't be surprised if Herron starts at running back again this week against the Redskins.
Wells didn't mention anything about beyond this week, but reading into it a bit, it would sure seem like Herron could end up being the starter over Richardson. Herron didn't need a lot of time to out-perform Richardson in practice and move into the starting role. Richardson will still get his carries which will likely cap Herron's fantasy value, but Herron seems like the back to own between the two.