Alonso (knee) had his practice period expire Saturday and will remain on the PUP list for the rest of the season, per the NFL's official transaction log.
The veteran linebacker was acquired by the 49ers from the Saints at the start of November, but he won't be returning from the PUP list this season. Alonso underwent surgery to repair a torn ACL in January and returned to practice Oct. 19, but he can't rejoin the active roster now that his designated practice period has expired.