San Francisco 49ers lose second starting left tackle in two weeks, with Colton McKivitz to miss two months with MCL sprain in knee 4:01 PM ET Nick WagonerESPN Staff Writer Close Covered Rams for nine years for stlouisrams.com Previously covered University of Missouri football Member of Pro Football Writers of America SANTA CLARA, Calif. -- For the second week in a row, the San Francisco 49ers have lost their starting left tackle to injury for an extended period. A little more than a week after star left tackle Trent Williams suffered a high right ankle sprain in a Sept. 25 loss to the Denver Broncos , Colton McKivitz departed Monday night's win against the Los Angeles Rams with a knee injury. On Tuesday afternoon, Niners coach Kyle Shanahan said further testing on McKivitz's knee confirmed the initial fears of an MCL sprain along the lines of the injuries that running back Elijah Mitchell and linebacker Azeez Al-Shaair have. "He's going to be out a while," Shanahan said. "It's very similar to what Elijah and Azeez have." Editor's Picks 49ers' Williams has high ankle sprain, out weeks 8d Nick Wagoner Going off of the timetable for Mitchell and Al-Shaair, McKivitz can be expected to miss about two months. This means the Niners will likely have to hold the fort at left tackle with third-stringer Jaylon Moore until Williams returns from what is expected to be a four-to-six-week absence. Moore replaced McKivitz against the Rams, playing the final 17 offensive snaps of the game. He has started three NFL games since the Niners used a 2021 fifth-round pick on the former Western Michigan lineman. Daniel Brunskill , who has started games at every spot on the Niners offensive line since 2019, is another possibility. "We'll see how this week plays out," Shanahan said. "We haven't really discussed it yet. Most likely it will be Jaylon Moore but we know Dan is always an option." Elsewhere on the injury front, defensive lineman Arik Armstead is dealing with a right foot and ankle injury, according to Shanahan. Armstead departed Monday night's game and did not return after missing the Denver game with the injury. Wide receiver Jauan Jennings sprained his ankle against the Rams and is considered day-to-day. In better Niners injury news, Shanahan said the team plans to open the practice window for free safety Jimmie Ward and cornerback Jason Verrett on Wednesday. Ward (hamstring) and Verrett (knee) have been on injured reserve and physically unable to perform lists, respectively, and this is the first week they are eligible to return.