It looks like LB Jeff Ulbrich's post-concussion issues were a bit too much bear at this point. The 49ers placed him on injured reserve and signed free agent LB Matt Wilhelm. I don't have a scouting report at this point on Wilhelm, other than to say he'll be playing inside linebacker, but in reality, probably mostly on special teams.
Wilhelm (6-4, 245) has seen action in 71 games (21 starts) since being drafted in the fourth round (112th pick overall) of the 2003 NFL Draft by the San Diego Chargers out of Ohio State. He spent six seasons with the Chargers (2003-08), totaling 247 tackles, six interceptions, two sacks, 13 passes defensed and 41 special teams stops. Wilhelm spent training camp with the Philadelphia Eagles in 2009, before being released prior to the season. He is a native of Oberlin, Ohio.
The big issue this raises is one of special teams. Ulbrich was a stalwart on special teams and will definitely be missed the rest of the season. If this marks the end of Ulbrich's career, it is a sad day. While he was never the most talented player on the field, he's definitely busted his butt his entire career, lasting ten years as a San Francisco 49er. Let's hope for the best for Jeff, whether he plays again or not.