The Rams informed Sullivan on Tuesday that they wouldn't exercise his $6 million team option for 2019, Lindsey Thiry of ESPN.com reports.
Sullivan is still a solid player despite his advanced age, so his release is likely only for cap-relief purposes. With the 33-year-old's salary off the books, the Rams are expected to turn to 2018 fourth-round pick Brian Allen as their first-string center when OTAs begin.