Havenstein (ankle) is doubtful to play in Thursday night's contest against the 49ers, Stu Jackson of the Rams' official website reports.
Havenstein was considered a non-participant on Monday's practice estimate and Tuesday's walkthrough, and then he was officially a non-participant at Wednesday's practice. If the 33-year-old is unable to go in Week 5, Warren McClendon and D.J. Humphries are the two top candidates to start at right tackle versus San Francisco.