Kendricks (toe) will be out for at least a month according to coach Kyle Shanahan, Matt Maiocco of NBC Sports Bay Area reports.
Kendricks didn't re-enter Sunday's preseason contest after picking up the injury in the first half. It is likely the 30-year-old will miss at least one regular season game as he rehabs. The 49ers currently have injuries to Kendricks, Dre Greenlaw (blister), Azeez Al-Shaair (knee) and Demetrius Flannigan-Fowles (concussion) -- their top four outside linebackers.