Coach Kyle Shanahan said Monday that Thompson (ankle) is not expected back for Week 5, Cam Inman of The San Jose Mercury News reports.
Thompson has already missed the 49ers' last two games with an ankle injury he picked up in Week 2 versus the Dolphins, and it seems like he's trending towards missing another contest come Sunday. In that case, Sebastian Valdez would be a candidate for increased snaps on the defensive line.