I think Wagoner summed up the most likely reason in the article Rambos just posted:
Freeing up cap room + possibility of signing him back to a non-guaranteed contact = smart financial move.Quote:
But here's the easy bottom line explanation. By releasing Dunbar now, the Rams can be cap-compliant tonight and it gives them the opportunity to bring him back after week one on a non-guaranteed contract. The suspension clock begins this week whether Dunbar is with a team or not. Week 5 is still the scheduled return date for Dunbar no matter what team he is on.
Theoretically, the Rams could bring him back next week on a non-guaranteed deal at a reduced rate, place him back on the reserve/suspended list and would then have him back in time for Week 5. They could also bring him back closer to the Oct. 6 game against Jacksonville when he'd again be eligible to play.