San Francisco 49ers‘ running back Raheem Mostert has been placed on the injured reserve list, according to Pro Football Talk's Mike Florio. With the move, the back will be unavailable for a minimum of three weeks, no thanks to the ankle injury he suffered during Sunday night's game against the Los Angeles Rams.

Though the move was expected all week, the official loss of Mostert is still discouraging for a team that has, thus far, been ravaged by injuries. Having sent 14 players to the IR through the first six weeks of the season, the Niners have struggled to gain consistency following their appearance in the Super Bowl.

Heavily reliant on Mostert as a key to their heavy play-action attack, San Francisco may have to adjust their offensive game plan further with quarterback Jimmy Garoppolo already struggling to stretch the field as the team did so effectively last season.

Without their starting half-back–who in four starts had gained 303 rushing yards with two touchdowns–the 49ers will likely rely on a committee of backs to fill the void, most noticeably Jerrick McKinnon and JaMychal Hasty, who have combined for just over 250 rushing yards on the year.

To fill out the roster following the loss of not only Mostert but both starting safeties–Jaquiski Tartt and Jimmie Ward– the team did announce the activation of safeties Johnathan Cyprien and Jared Mayden from the practice squad. While the injuries are not expected to be long-term, the absence of the defensive players only lessens the margin of error the Niners possess heading into their game against the New England Patriots.