Atogwe knew this was a distinct possibility, given the nature of his contract. He had an $8 million roster bonus due Feb. 21, which in essence forced a decision from the Rams, who have used their franchise tag on Atogwe in the past and re-signed him as a free agent last year.
"This is a decision we have made at this time with O.J. We will continue to explore all of our options at the safety position like we will with every other position on our football team," said Rams general manager Billy Devaney in a statement Friday.
Atogwe now is free to negotiate and sign with any team.
Atogwe remains open to a return with the team that drafted him in the third round of the 2005 NFL Draft.
Atogwe, a six-year veteran, started 15 games in 2010 and finished with 73 tackles, two sacks, two forced fumbles and three interceptions.