Finnegan sat out practice this week with an eye injury. According to Nick Wagoner of ESPN.com, the nature of Finnegan’s injury is unclear.
The 4-6 Rams host Chicago on Sunday.
Finnegan, 29, played seven games for St. Louis in 2013, intercepting one pass and making 27 tackles. He signed with the Rams as a free agent in March 2012.
To fill Finnegan’s roster spot, the Rams promoted safety T.J. McDonald from the injured reserve/designated for return list, Thomas said.
McDonald started the first four games of 2013 for St. Louis, recording 18 tackles. He suffered a broken leg in the Rams’ Week Four loss to San Francisco.