The 49ers signed Walker to the active roster Wednesday.
Walker has been on the 49ers' practice squad this season, and he's been elevated to the active roster twice. The 27-year-old linebacker now has some security on the 53-man roster. He likely won't play much on defense barring an injury, but it's noteworthy that Kwon Alexander is dealing with an ankle injury. If Alexander misses time, Walker could log a handful of snaps.