Mostert suffered a left high-ankle sprain in Sunday night’s win over the Los Angeles Rams that will “most likely” land him on IR, per Nick Wagoner of ESPN.com.
Additionally, Garland sustained a calf strain that will send him to the injured list as well.
Mostert left the game against the Rams early in the third quarter after a 1-yard run that ended with him catching his left leg awkwardly underneath him.
Garland left late in the fourth quarter as he came up favoring his right leg after a play when he was blocking Rams defensive tackle Aaron Donald. Hroniss Grasu took over at center in Garland’s absence.
The injured reserve only requires missing three weeks this season but Shanahan said that it’s possible the recovery is longer than that for Mostert.
“We’ll see how it progresses,” Shanahan said.
Mostert leads the 49ers this season with 303 yards on 51 carries. The 49ers also have Tevin Coleman (knee) and Jeff Wilson Jr. (calf) dealing with injuries at the position as well. That could leave just Jerick McKinnon and JaMychal Hasty to handle the job this week against the New England Patriots.