The 49ers placed running back JaMycal Hasty and safety Johnathan Cyprien on injured reserve Tuesday, the team announced.
Hasty broke his collarbone on his 15th offensive snap Sunday and Cyprien injured his hamstring on his second special teams snap.
The 49ers currently have 16 players on injured reserve.
Safety Jared Mayden went on the practice squad injured reserve list. He joins receiver Jauan Jennings on the practice squad injured reserve list.
He was obtained from New Orleans to offset some of Alexander’s salary and becomes a free agent after this season.
Alonso is on the physically unable to perform list and not ineligible to play with his practice period having expired.