The Hawks have released Chris Matthews.
Richardson has a hamstring and Irvin apparently has an MCL sprain.
Edit:
Just some information, but Christine Michael was cut by the Cowboys today, too.
He was said to have the most talent of the RB's in his draft year, but he didn't seem to be able to "get it".
Just speculation on my part, but maybe he isn't too bright or doesn't want to put in the work.