With six players on the shelf with injuries, the St. Louis Rams' offensive line took another hit this week when backup guard/center Mark Setterstrom left Friday's mini-camp practice with a "visible knot" above his left elbow.

The prognosis: Torn triceps muscle, which may end Setterstrom's season, Bill Coats of the St. Louis Post-Dispatch reports.

Setterstrom's injury history played a role in the Rams' decision to not extend a qualifying offer to the restricted free agent this off-season, instead signing him to a one-year deal for the veteran minimum, with incentives and a roster bonus increasing the total value of the deal.

A seventh-round pick (242nd overall) out of the University of Minnesota in 2006, Setterstrom started six games his rookie season, and opened 2007 as the starting left guard before a knee injury landed him an injured reserve. Setterstrom missed the entire 2008 season after injuring his knee during training camp.

Brought back on a one-year deal for 2009, Setterstrom's season ended in Week 16 with a torn triceps muscle, the same one he injured on Friday.