According to the Lions official injury report, Theo Riddick will not play Week 7.
Fantasy Impact:
You hopefully weren't starting Riddick anyway, so the main thing to look at here is how his absence will affect Kerryon Johnson and LeGarrette Blount. The latter isn't likely to see any change in usage, as he wasn't playing on third downs anyway. Johnson, on the other hand, figures to add Riddick's role to his own, making for an interesting mid-range RB2 in a juicy matchup against the Dolphins.